Showcase No. 6
January-February 1957
Cover: Challengers freeing monster from giant egg //Jack Kirby / Marvin Stein
Story: “The Secrets of the Sorceror’s Box” (chapter 1; 6 pages)
 Chapter 2: “Dragon Seed” (6 pages)
 Chapter 3: “The Freezing Sun” (6 pages)
 Chapter 4: “The Whirling Weaver” (6 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Intro and origin: The Challengers of the Unknown (Professor Mark “Prof” Haley (first name revealed in CHALLENGERS OF THE UNKNOWN #83), Red Ryan, Rocky Davis, Ace Morgan (last chronological appearance for all in flashback in CHALLENGERS OF THE UNKNOWN #31))
Villains: Morelian (first appearance; dies in this story), a giant (first appearance; destroyed in this story), a negative sun (first and only appearance)
Comment: The earlier chronological appearances of Prof, Red, Rocky, and Ace are as follows:
 Ace Morgan’s war exploit (CHALLENGERS OF THE UNKNOWN #45 (fb))
 Ace Morgan appears at an air show during Superboy’s public debut (NEW ADVENTURES OF SUPERBOY #1 (fb))
 Rocky Davis wrestles Barton, Prof Haley recovers a sunken statue, Red Ryan builds a giant transmitter, and Ace Morgan helps dynamite a mountain (CHALLENGERS OF THE UNKNOWN #31 (fb))
Synopsis: Four men survive an airplane crash that should have killed them, and decide that they are “living on borrowed time”.  Accordingly, they band together and form the Challengers of the Unknown, a group of daredevils who take on the riskiest assignments.  Their first challenge as a group comes from a sorceror named Morelian, who hires them to open an ancient box from which four menaces come forth.

Showcase No. 7
March-April 1957
Cover: Challengers and June Robbins vs. Ultivac //Jack Kirby / Marvin Stein
Story: “Ultivac Is Loose” (chapter 1; 7 pages)
 Chapter 2: “A Challenger Must Die” (6 pages)
 Chapter 3: “The Fearful Millions” (6 pages)
 Chapter 4: “The Fatal Prediction” (6 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Feature Characters: The Challengers of the Unknown (next appear in issue #11)
Supporting Character: June Robbins (first appearance; next appears in CHALLENGERS OF TE UNKNOWN #1)
Villains: Ultivac (a robot; first appearance; next appears in DC COMICS PRESENTS #77), Felix Hesse, Floyd Barker
Comment: June’s hair is black in this story, but is colored blonde in all future stories.
Synopsis: The Challengers must face a giant computer-robot, Ultivac, created by an ex-Nazi scientist but now obedient only to himself.

Showcase No. 11
November-December 1957
Cover: Challengers watching Gen. Tolek blow up model Earth //Jack Kirby / Marvin Stein
Story: “The Day the Earth Blew Up” (chapter 1; 7 pages)
 Chapter 2: “The Tyrans” (6 pages)
 Chapter 3: “The Thing That Came Out of the Sea” (6 pages)
 Chapter 4: “One Minute To Doom” (5 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Feature Characters: Challengers of the Unknown (last appearance in issue #7)
Intro: Carl Jackson, Warren Moss, Commander Lockwood, Colonel Price (only appearance for all)
Villains: Gen. Tolek, Garnat, and other Tyrans (first appearance for all; all die in this story)
Synopsis: The Challengers search for two scientists missing in the Antarctic and come across an alien race preparing to invade and conquer Earth.

Showcase No. 12
January-February 1958
Cover: Challengers vs. giant squid //Jack Kirby / Marvin Stein
Story: “The Menace of the Ancient Vials” (chapter 1; 6 pages)
 Chapter 2: “The Fire Being” (6 pages)
 Chapter 3: “The Demon From the Depths” (6 pages)
 Chapter 4: “The Deadly Duplicates” (6 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Feature Characters: Challengers of the Unknown (next appear in CHALLENGERS OF THE UNKNOWN #1)
Intro: Amos Hunter, Chet Hollister, Dr. Rodney (only appearance for all)
Villains: Karnak, a kraken (first and only appearance for both), Brommer, Gortz, a Fire Being (first appearance for all; all die in this story)
Synopsis: An international criminal acquires vials containing sorceror’s potions which can expand a person’s size, create a fire being, or create duplicates of its drinker, and the Challengers of the Unknown must combat him.

Challengers of the Unknown No. 1
April-May 1958
Cover: Challengers in transparent box, menaced by alien child’s pet //Jack Kirby / Marvin Stein
Story: “The Man Who Tampered With Infinity” (15 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Feature Characters: Challengers of the Unknown (last appearance in SHOWCASE #12)
Supporting Character: June Robbins (mistakenly called June Walker in this story; last appearance in SHOWCASE #7)
Villains: Olan Tagorian and his gang (first and only appearance for all)
Synopsis: The Challengers meet a criminal scientist whose “infinity machine” teleports monsters from other dimensions to Earth.

Story: “The Human Pets” (10 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Feature Characters: Challengers of the Unknown
Intro: Abner and Myrtle Jenkins, an alien boy and his parents (only appearance for all)
Synopsis: The Challengers are lured into a space probe which proves to be a capturing device for an alien boy’s “animal” collection.

Challengers of the Unknown No. 2
June-July 1958
Cover: Giant hands reaching for the Challengers’ aircraft //Jack Kirby / Marvin Stein
Story: “The Monster Maker” (14 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Feature Characters: Challengers of the Unknown
Intro: Dr. Hascomb (only appearance)
Villain: Roc (first and only appearance)
Synopsis: When a criminal gains control of a mind-over-matter machine, the scientist who created it gives Ace similar powers with which to fight him.

Story: “The Traitorous Challenger” (10 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (still mistakenly called June Walker in this story)
Intro: Digger Bill (only appearance)
Villain: An atomic beast (first appearance; dies in this story)
Synopsis: The Challengers cannot fathom why June Robbins is deliberately sabotaging their attempts to deal with a monster, until they learn that she has seen a computer predict that they will die if they battle the beast.

Challengers of the Unknown No. 3
August-September 1958
Cover: Ace, June, Prof, and Red watching Rocky melt his way out of space capsule //Jack Kirby / Marvin Stein
Story: “The Secret of the Sorcerer’s Mirror” (12 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein

Feature Characters: Challengers of the Unknown
Intro: Kregon the Sorceror (in flashback), a genie (only appearance for both)
Villains: Hillary Mycroft and his gang (first and only appearance for all)
Synopsis: The Challengers must stop a criminal from assembling an ancient sorceror’s apparatus which will give him incredible magic powers.

Story: “The Menace of the Invincible Challenger” (13 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Marvin Stein
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (still called June Walker in this story)
Intro: Professor Curtis (only appearance)
Villains: Chopper, Roxie, and another crook (first and only appearance for all)
Synopsis: Rocky ingests an alien chemical that gives him super-powers, but also drives him insane.

Challengers of the Unknown No. 4
October-November 1958
Cover: Darius Tiko trapping Challengers with anti-gravity ray //Jack Kirby / Wally Wood
Story: “The Wizard of Time” (Chapter 1; 6 pages)
 Chapter 2: “The Men Who Rode Across the Sun” (5 pages)
 Chapter 3: “The Sorcerer’s Sect” (7 pages)
 Chapter 4: “The Mechanical Judge” (7 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Wally Wood
Feature Characters: Challengers of the Unknown
Intro: Prof. Harlan Fuller, Rhamis (only appearance for both), Nostradamus (of Earth-One)
Villains: Darius Tiko, a Greek oracle (first and only appearance for both)
Comment: Shortly after this story, the Challengers probably battle Hunzar for the first time as shown in flashback in the second story in issue #10.
Synopsis: A scientist named Darius Tiko discovers a time cube which can transport him to ancient times and the far future.  But his plans to take weapons from the future and bring them to the present in order to conquer Earth put him at odds with the Challengers.

Challengers of the Unknown No. 5
December 1958 / January 1959
Cover: Vreedl vs. Challengers and June Robbins //Jack Kirby / Wally Wood
Story: “Riddle of the Star-Stone” (25 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Wally Wood
Feature Characters: Challengers of the Unknown (next chronological appearance in flashback in JUSTICE LEAGUE OF AMERICA #144)
Supporting Character: June Robbins
Comment: Shortly after this story the Challengers help the heroes of Earth deal with Commander Blanx and his Martians, as shown in JUSTICE LEAGUE OF AMERICA #144 (flashback).

Challengers of the Unknown No. 6
February-March 1959
Cover: Ace and Prof watching June Robbins and sorceror turn Rocky and Red to stone //Jack Kirby / Marvin Stein
Story: “Captives of the Space Circus” (15 pages)
Editor: Jack Schiff
Writer, penciller: Jack Kirby
Inker: Wally Wood
Feature Characters: Challengers of the Unknown (last chronological appearance in JUSTICE LEAGUE OF AMERICA #144 (flashback))
Intro: Round men, flying men (aliens; only appearance for all)
Villains: Tartan and the Stupendous Interplanetary Circus (first and only appearance for all)
Synopsis: The Challengers are kidnapped by aliens and forced to perform in an interplanetary circus.

Story: “The Sorceress of Hidden Valley” (10 pages)
Editor: Jack Schiff
Plotter, penciller: Jack Kirby
Scripter: France Herron
Inker: Wally Wood
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins

Challengers of the Unknown No. 7
April-May 1959
Cover: Giant alien hand trapping Challengers in butterfly net //Jack Kirby / Marvin Stein
Story: “Isle of No Return” (13 pages)
Editor: Jack Schiff
Plotter, penciller: Jack Kirby
Scripter: France Herron
Inker: Wally Wood
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins

Story: “The Beasts From Planet Nine” (12 pages)
Editor: Jack Schiff
Plotter, penciller: Jack Kirby
Scripter: France Herron
Inker: Wally Wood
Feature Characters: Challengers of the Unknown

Challengers of the Unknown No. 8
June-July 1959
Cover: Juhl encasing Challengers in spheres //Jack Kirby / Marvin Stein
Story: “The Man Who Stole the Future” (12 pages)
Editor: Jack Schiff
Plotter, penciller: Jack Kirby
Scripter: France Herron
Inker: Wally Wood
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Intro: Marie (only appearance)
Villain: Drabny (first appearance; next appears in issue #42)
Synopsis: A villain named Drabny steals inventions from the future to gain power in the present, and the Challengers take a hand against him.

Story: “The Prisoners of Robot Planet” (13 pages)
Editor: Jack Schiff
Plotter, penciller: Jack Kirby
Scripter: France Herron
Inker: Wally Wood
Feature Characters: Challengers of the Unknown
Intro: Juhl and other Zunians (first and only appearance)
Villain: Kra (first appearance; next appears in issue #42), other robots (first and only appearance for all)
Comment: Even though Kra’s internal mechanisms are dismantled in this story, he is evidently somehow reassembled before issue #42.
Synopsis: Juhl, an alien from the planet Zuna, comes to Earth to bring the Challengers to his world so that they may defeat the tyrant robots that have conquered his people.

Challengers of the Unknown No. 9
August-September 1959
Cover: Mole creature blasting hole in ground below Challengers  //Bob Brown
Story: “The Men Who Lost Their Memories” (10 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (last appearance in issue #?)
Intro: Martin Ferndale, Higgins (only appearance for both)
Villains: Dekkar and his gang (first and only appearance for all)
Synopsis: When a villain named Dekkar uses a machine to steal the Challengers’ memories, June Robbins must show her amnesiac friends how to defeat their foe.

Story: “The Plot To Destroy Earth” (14 pages)
Editor: Jack Schiff
Writer:
Penciller: Bob Brown
Inker: Wally Wood?
Feature Characters: Challengers of the Unknown
Villains: Three alien creatures (first appearance for all; all die in this story), three robots (first and only appearance for all)
Synopsis: The Challengers stumble upon an alien plot to dismantle the Earth by means of three destructive creatures.

Challengers of the Unknown No. 10
October-November 1959
Cover: Challengers in bathyscaph seeing their faces on an underwater hill while giant robot hand menaces them //Bob Brown
Story: “The Cave-Man Beast” (12 pages)
Editor: Jack Schiff
Writer: Arnold Drake?
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (becomes a brunette in this story)
Villain: Dr. Manning (first and only appearance)
Synopsis: A scientist is transformed into a giant, super-strong, rampaging caveman, and the Challengers and June Robbins must find a way to subdue him.
 
Story: “The Four Faces of Doom” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: X-2 (first and only appearance)
Villains: Hunzar and his men (first and only appearance for all)
Comment: The flashback portion of this tale probably takes place between issues #4 / 5.
Synopsis: The Challengers are transported through time by a beautiful rebel to make war against a tyrant.

Challengers of the Unknown No. 11
December 1959 / January 1960
Cover: Zarx on flying creature attacking the Challengers //Bob Brown (wash drawing)
Story: “The Creatures From the Forbidden World” (chapter 1; 10 pages)
 Chapter 2: “The Land Beyond the Light” (6 pages)
 Chapter 3: “The Achilles Heel” (10 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (back to blonde hair in this story)
Intro: Prof. Markson, Spaatz, Cleary, Barda (not to be confused with Big Barda of MR. MIRACLE), Srella, Aktonians (only appearance for all)
Villains: Zarxes (first and only appearance)
Synopsis: The Challengers are transported to an extradimensional world to help its inhabitants overthrow the conquering Zarxes, who wish to enslave Earth as well.

Challengers of the Unknown No. 12
February-March 1960
Cover: Challengers and S’ntaga vs. alien giant //Bob Brown
Story: “The Challenger From Outer Space” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: S’ntaga, Krandanians (only appearance for all)
Villains: Alien giants (first and only appearance)
Synopsis: An alien hero comes to Earth to help the Challengers cope with menacing four-armed giants.

Story: “The Three Clues To Sorcery” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Villain: Dr. Fenton and his gang (only appearance)
Comment: In this story, the Challengers gain their new headquarters inside Challenger Mountain.
Synopsis: A criminal scientist kidnaps June Robbins to force the Challengers into finding three objects that will give him untold power.

Challengers of the Unknown No. 13
April-May 1960
Cover: Rocky with Golden Fleece, riding centaur towards Ace and Red as Prof watches //Bob Brown
Story: “The Prisoner of the Tiny Space Ball” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Zanna, Vraba, Benrun, Ak-Selians (only appearance for all)
Villains: Dakyab and his men (first and only appearance for all)
Synopsis: The Challengers free an alien deportee from his prison within a tiny ball, then go with him to liberate his planet from a tyrant.

Story: “The Creatures From the Past” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (again a brunette)
Intro: Dr. Henry (only appearance)
Villains: A cyclops, a centaur, a dragon (first appearance for all; all destroyed in this story)
Synopsis: The Challengers accompany June and a scientist on a quest for the real Golden Fleece.  But when Rocky discovers it and dons it, it turns him malevolent and gives him strange powers.

Challengers of the Unknown No. 14
Cover: Two K’zanas, June Robbins, Prof, and Red in cage, and Rocky and Ace in beam //Bob Brown
Story: “The Man Who Conquered the Challengers” (12 pages)
Editor: Jack Schiff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Dr. Charles Ferris, Miss Landreu (only appearance for both)
Villain: Multi-Man (Duncan Pramble; first appearance; next appears in issue #15)
Synopsis: An archaelogist’s crooked assistant concocts an alchemical formula, “liquid light”, from an old manuscript.  It gives him the power to transform himself into many different powerful forms, making him a Multi-Man, and the Challengers have to oppose him.

Story: “Captives of the Alien Beasts” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Intro: Two K’zanas (alien beasts), two aliens (first and only appearance for all)
Synopsis: The Challengers and June Robbins are teleported to an alien world by a giant beast running amuck.

Challengers of the Unknown No. 15
August-September 1960
Cover: Giant June Robbins wrestling monster as Challengers look on //Bob Brown
Story: “The Return of Multi-Man” (15 pages)
Editor: Jack Schiff
Writer: France Herron?
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Brannigan, Sanders (only appearance for both)
Villains: Multi-Man (next appears in issue #20), Gurk (first and only appearance)
Comment: Multi-Man evolves into his final, big-headed form in this story.
Synopsis: Multi-Man breaks out of jail, and a criminal collector named Gurk employs him to find three pieces to a golden turtle statuette that can reveal the whereabouts of a treasure.  The Challengers are out to stop them both.

Story: “The Lady Giant and the Beast” (10 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Intro: A microbe monster (only appearance)
Synopsis: Strange microbes turn June Robbins and a microscopic monster into giants, making life dangerous for the Challengers.

Challengers of the Unknown No. 16
October-November 1960
Cover: Challengers in force-sphere, Halanka, Thark //Bob Brown
Story: “The Incredible Metal Creature” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Thark (only appearance)
Villains: Albom, Halanka (first and only appearance for all)
Synopsis: Pursuing a criminal, the Challengers encounter a metallic fugitive from another world.  An interplanetary lawman comes to their aid.

Story: “Prisoners of the Mirage World” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Intro: Sir Manson, Melissa, and other inhabitants of the Mirage World (only appearance for all)
Villain: Sir Rodford (only appearance)
Synopsis: June Robbins steps into a world apparently within a mirage, with a medaeval culture, and the Challengers follow to try to rescue her.

Challengers of the Unknown No. 17
December 1960 / January 1961
Cover: Zod causing lighthouse to collapse towards Challengers  //Bob Brown
Story: “The Genie Who Feared June” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Villains: Malvolio and his gang, Ahmed (a genie; first and only appearance for all)
Synopsis: The Challengers must battle a villain and the ancient genie whom he unleashes on them, but the genie turns out to be inexplicably afraid of June Robbins.

Story: “Secret of the Space Capsules” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Zod (a beast), two aliens (first and only appearance for all)
Synopsis: The Challengers learn from two aliens, frozen on Earth since the Ice Age, that they must somehow stop great menaces the aliens brought with them.

Challengers of the Unknown No. 18
February-March 1961
Cover: Challengers and Dr. Oren Gough vs. cosmic creature //Bob Brown
Story: “The Menace of Mystery Island” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Characters: June Robbins,  Cosmo (J’suna; the Challengers’ pet; first appearance; real name revealed in issue #32;  next appears in issue #21)
Villains: A gang of crooks (first and only appearance)
Synopsis: The Challengers find a strange alien pet in a space capsule from another world on their way to an island June has inherited, and which is used by crooks as a weapons depot.

Story: “The Doomed World of Tomorrow” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Dr. Oren Gough
Villains: Lenroy (first and only appearance), his robots, cosmic creatures (first appearance for all; all destroyed in this story)
Synopsis: The Challengers are accidentally yanked into the future to help the inhabitants of Earth defeat some cosmic creatures.

Challengers of the Unknown No. 19
April-May 1961
Cover: Challengers and June Robbins vs. Roney and two monsters //Bob Brown
Story: “The Alien Who Stole a Planet” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Lyo, Ia (only appearance for both)
Villains: Bara, Oji, and other aliens (first and only appearance for all)
Comments: The Challengers encounter aliens from a “Noah’s Ark” ship containing the recorded essence of an entire world’s population, but a power-hungry member of the crew uses the recording device to take over the ship and attack the heroes.

Story: “The Beasts From the Fabulous Gem” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (back to blonde hair)
Intro: A wizard (only appearance)
Villains: Roney, two monsters (first and only appearance for all)
Synopsis: In a remote valley, a criminal gains control of a sorceror’s stone enabling him to control two monsters and comes into conflict with the Challengers.

Challengers of the Unknown No. 20
June-July 1961
Cover: Giant Rocky, Prof, June Robbins and Ace vs. giant green killer whale //Bob Brown
Story: “Multi-Man Strikes Again” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villain: Multi-Man (between issues #15 / 24) and his gang
Synopsis: Multi-Man escapes from jail and uses super-scientific devices to compensate for his lost powers.

Story: “The Cosmic-Powered Creatures” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (a brunette again)
Intro: Captain Carlson (only appearance)
Synopsis: The Challengers attempt to rescue a crashed astronaut whose irradiated space suit causes incredible mutations.

Challengers of the Unknown No. 21
August-September 1961
Cover: Challengers, June Robbins, and Cosmo vs. dragon //Bob Brown
Story: “The Weird World That Didn’t Exist” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Intro: Albert D. Farnum (only appearance)
Villains: A gang of crooks (first and only appearance)
Synopsis: A surprise that June Robbins and a group of moviemakers plan for the Challengers goes awry when criminals hijack the high-tech equipment and use it against the heroes.

Story: “The Challengers’ Space-Pet Ally” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: Cosmo (between issues #18 / 25), June Robbins
Intro: Henry Perkins, Emma Perkins (only appearance for both)
Villains: Zardoc and his gang (first and only appearance for all)
Synopsis: A criminal mystic, Zardoc, gains mind-over-matter powers from a strange meteorite, but the Challengers employ their space-pet Cosmo to even the odds.

Challengers of the Unknown No. 22
October-November 1961
Cover: Monstus vs. Challengers and June Robbins //Bob Brown
Story: “The Curse of the Golden God” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Hinton, Jarvis (first and only appearance for both)
Synopsis: The Challengers battle two explorers who appear to have gained great powers and become slaves of the god Xechulan.

Story: “The Thing In Challenger Mountain” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Intro: An alien lawman, four time-lost warriors (only appearance for all)
Villains: J’kal, Monstus (first and only appearance for both)
Synopsis: The Challengers and June Robbins are captured by an alien who steals people from other time periods for his “zoo”.

Challengers of the Unknown No. 23
December 1961 / January 1962
Cover: Zog and other aliens attacking Challengers and June Robbins (in plane) with ray //Bob Brown
Story: “Death Guarded the Doom Box” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Burt Langdon and his gang (first and only appearance for all)
Comment: This is the first 12-cent issue.
Synopsis: The Challengers brave a gauntlet of ancient traps in order to beat a criminal to a wizard’s deadly device.

Story: “The Island In the Sky” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins
Intro: Dr. Kue, Greeg (only appearance for both)
Villains: Zog and his men (first and only appearance for all)
Synopsis: The Challengers are contacted by two alien scientists who warn them of the menace of Zog, a criminal of their world who has stolen a sky platform.

Challengers of the Unknown No. 24
February-March 1962
Cover: Multi-Man (in energy form) vs. Challengers and June Robbins //Bob Brown
Story: “The Challengers Die at Dawn” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (blonde in this story)
Intro: Banjuk tribesmen (only appearance)
Villain: Manfredo (first and only appearance)
Synopsis: The Challengers, on the trail of a criminal in the Oriental jungle, defy a tribal taboo and must undergo a gauntlet of deadly tests.

Story: “Multi-Man, Master of  Earth” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (back to brunette)
Villains: Multi-Man (between issues #20 / 30) and his gang (first and only appearance)
Synopsis: Multi-Man regains his old powers through use of a special pill, and the Challengers must stop him from conquering the Earth.

Challengers of the Unknown No. 25
April-May 1962
Cover: Kubagy, Challengers and June Robbins in dome, and Cosmo //Bob Brown
Story: “Return of the Invincible Pharaoh” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Lasandra (in flashback; dies in this story), Tut Aba (dies in this story)
Villains: Torbert and his gang (first and only appearance)
Synopsis: The Challengers encounter an ages-old Pharaoh who has been preserved and given great powers by a “life liquid” which is now in the hands of a criminal.

Story: “Captives of the Alien Hunter” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Characters: June Robbins, Cosmo (between issues #21 / 33)
Intro: Mr. Felix, Joe and other Boy Scouts (only appearance for all)
Villains: Kubagy (first and only appearance) and his robot (first appearance; destroyed in this story)
Synopsis: An alien comes to Earth in search of chlorine to power his super-robot, but the Challengers and their space-pet Cosmo oppose him.

Challengers of the Unknown No. 26
June-July 1962
Cover: Aqua-beast menacing June Robbins, Rocky, and Ace //Bob Brown
Story: “Death Crowns the Challenger King” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: King Moyata, Ulsing (only appearance for both)
Villains: Kidamina and his minions (first and only appearance for all)
Synopsis: In a lost valley, Prof takes the place of a look-alike prince to run a gauntlet of tests which could prove deadly--and, if conspirators against the crown have their way, definitely will.

Story: “The Secret of the Space Spectaculars” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (next appears in issue #28)
Intro: Kandu (only appearance)
Villains: A gang of alien criminals, a Kandu impersonator (first and only apperance for all)
Synopsis: The Challengers meet a magician who proves to be an alien policeman, in search of three pods planted by criminals from his planet which hatch destructive beasts.

Challengers of the Unknown No. 27
August-September 1962
Cover: Dr. Edward Gruner, Challengers, and Volcano Man //Bob Brown
Story: “The 1,001 Impossible Inventions” (12 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Mr. King (only appearance)
Villains: Kleeg, Lowther, Gates (first and only appearance for all)
Comment: This issue contains the first Challengers Mail Chute letters column.
Synopsis: The Challengers take on a pair of crooks who have been given super-scientific equipment by an alien they have befriended.

Story: “Master of the Volcano Men” (13 pages)
Editor: Jack Schiff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villain: Volcano Men I and II (first appearance; both next appear in issue #32) and other Volcano Men, Dr. Edward Gruner (first and only appearance for all)
Synopsis: The Challengers must deal with monsters composed of flaming volcanic rock unleashed by a criminal scientist.

Challengers of the Unknown No. 28
October-November 1962
Cover: Challengers, June Robbins, and Egyptians in ancient Egypt //Bob Brown
Story: “The Revolt of the Terrible FX-1" (11 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Dr. Harwyn, Omni-Fax (a computer; only appearance for both)
Villain: FX-1 (a robot; first appearance; destroyed in this story)
Synopsis: A powerful robot goes independent and berserk when lightning strikes it, and the Challengers must find a way to destroy it.

Story: “Riddle of the Faceless Man” (14 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (now a redhead; last appearance in issue #26)
Intro: Tushatta (in flashback; dies in this story), a pharaoh,  Princess Tahatsu, Myceraphis (only appearance for all)
Villains: Amenothoth and his men (first and only appearance for both)
Synopsis: The Challengers are teleported back in time to solve the mystery of five statues bearing their own and June Robbins’s likeness, and to rescue June from an Egyptian villain.
 
Challengers of the Unknown No. 29
December 1962 / January 1963
Cover: Rocky, Prof, and Marintels riding sea-horses underwater; Ace and Red menaced by Lavanite underground (two vignettes)  //Bob Brown
Story: “Four Roads To Doomsday” (14 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Dr. Wayne Dutro, alien lawmen (only appearance for all)
Villains: Suboko and other alien criminals (first and only appearance for all)
Synopsis: The Challengers, at the behest of an alien, neutralize four devices on the Earth’s highest, lowest, hottest, and coldest points, not knowing that by doing so they are priming the world for invasion.

Story: “The War Between the Challenger Teams” (11 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Marintels, Lavanites (only appearance for all)
Synopsis: Two Challengers apiece are captured by warring races, the merman Marintels and the subterranean Lavanites, and each seeks to aid their captors against their enemy.

Challengers of the Unknown No. 30
February-March 1963
Cover: Challengers (Prof in helicopter) using tank against Multi-Man //Bob Brown
Story: “Multi-Man--Villain Turned Hero” (13 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Dr. Lundy (only appearance)
Villain: Multi-Man (between issues #24 / 34)
Synopsis: An amnesiac Multi-Man turns his great intellect to good and becomes an ally of the Challengers, until an electric shock restores his memory and his evil nature.

Story: “The Fifth Challenger” (13 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Characters: June Robbins (a blonde again; next appears in issue #33),  F. Gaylord Clayburn III (first appearance; next appears in SUPER-TEAM FAMILY #10)
Villains: The Boss and his gang (first and only appearance for all)
Synopsis: Gaylord Clayburn, a playboy who escaped a near-fatal racing accident, seeks to prove to the Challengers that he has the skills to be their fifth member.

Challengers of the Unknown No. 31
April-May 1963
Cover: Rocky and Ace helping Wilfred Clayton assemble giant statue while bound Prof and Red look on //Bob Brown
Story: “The Man Who Saved the Challengers’ Lives” (chapter 1; 7 pages)
 Chapter 2: “The Secret From the Challengers’ Past” (6 pages)
 Chapter 3: “The Warrior From 1000 A.D.”  (12 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (origin details revealed in flashbacks, preceding their appearance in SHOWCASE #7; first chronological appearances for Rocky, Prof, and Red; Ace’s appearance chronologically between NEW ADVENTURES OF SUPERBOY #1 / SHOWCASE #7)
Intro: Sir Lawrence Revere, Staley (both in flashback), Dr. Steuben (only appearance for all)
Villains: Barton, Domingo (in flashback), Wilfred Clayton (first and only appearance for all), a gunman (first appearance; in flashback; dies in this story)
Synopsis: The Challengers meet a man who claims to have saved their lives after the plane crash that led to their banding together, and asks their help in assembling a giant robot--which he intends to use for criminal purposes.

Challengers of the Unknown No. 32
June-July 1963
Cover: Challengers and Volcano Man  //Bob Brown
Story: “One Challenger Must Die” (10 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Volcano Men I and II (combine to form Volcano Man; last appearance in issue #27; Volcano Man next appears in issue #45)
Synopsis: The Challengers disagree as to how to stop the two Volcano Men, and split into two teams to try and find ways of vanquishing one Volcano Man apiece.

Story: “Cosmo Turns Traitor” (15 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: Cosmo (last appearance in issue #25; last appearance)
Intro: D’jann (only appearance)
Villains: Mastermind and his gang (first and only appearance for all)
Synopsis: Cosmo’s master comes from outer space in search of his pet, but a criminal convinces the alien that the Challengers who harbor him are a band of evildoers.

Challengers of the Unknown No. 33
August-September 1963
Cover: Jacquard vs. Challengers //Bob Brown
Story: “The Challengers Meet Their Master” (13 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (between issues #30 / 35)
Villain: Jacquard (first and only appearance)
Synopsis: A criminal named Jacquard vows to defeat each of the Challengers at their specialties.

Story: “The Threat of the Trojan Robot” (12 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Raymond (a robot; first appearance; destroyed in this story), Larue (first and only appearance for both)
Synopsis: A scientist creates a robot Challenger as a gift to the Challengers, but he has ulterior motives.

Challengers of the Unknown No. 34
October-November 1963
Cover: Challengers, Multi-Man, and Multi-Woman //Bob Brown
Story: “Beachhead, U.S.A.” (10 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: The Nazis
Synopsis: The Challengers must stop a sub full of Nazis frozen for 18 years from using a bomb to blow up the Eastern seaboard.

Story: “Multi-Woman, Queen of Disaster” (chapter 1; 6 pages)
 Chapter 2: “Queen of a Thousand Threats” (9 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Multi-Man (between issues #30 / 40), Multi-Woman (a robot; first appearance; blown up in this story, but rebuilt for her next appearance, in issue #45)
Synopsis: Multi-Man breaks out of jail again, seeks to start his own nation, and creates a robot giantess named Multi-Woman to help him destroy the Challengers.

Challengers of the Unknown No. 35
December 1963 / January 1964
Cover: Challengers vs. Moon-Beast  //Bob Brown
Story: “War Against the Moon-Beast” (13 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Two aliens (in flashback), Dr. Lloyd Warner (only appearance for all)
Villain: The Moon-Beast (first and only appearance)
Synopsis: The Challengers witness a scientist’s laser experiment rousing a powerful Moon-Beast, which comes to Earth and runs rampant.

Story: “Sons of the Challengers” (12 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (between issues #33 / 46)
Intro: Madame Zaddum (next appears in issue #39)
Cameo appearances: The Sons of the Challengers (Paul Haley, Roxanne “Roxy” Davis, Red Ryan, Jr., Prof Haley, Jr.), Mrs. Red Ryan, Mrs. Rocky Davis, Mrs. Prof Haley (first appearance for all; as characters in a crystal ball vision; all next appear in issue #39), the Flying Fishmen (first and only appearance)
Comment: This is the first of the Sons of the Challengers stories.  The next appears in issue #39.
Synopsis: After the Challengers save the circus in which she works from disaster, fortune teller Madame Zaddum treats them to a vision of their possible future as sires of four children who fight the criminal Flying Fishmen as the Sons of the Challengers.

Challengers of the Unknown No. 36
February-March 1964
Cover: Ace, Prof, and Red trying to chain a giant Rocky //Bob Brown
Story: “The Giant In Challenger Moonbrain” (12 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Helen and her boyfriend (only appearance for both)
Villains: Krager and his gang (first and only appearance for all)
Synopsis: While chasing a criminal, Rocky falls into a stream filled with strange chemicals that later cause him to become a rampaging giant.

Story: “Bodyguards To a Star” (10 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Connie Baylor, Mark Faye, Teletype Thompson (only appearance for all)
Villain: Dane Cary (first and only appearance)
Synopsis: The Challengers must protect movie star Connie Baylor from near-fatal “accidents” on the scene of her latest picture, while trying to figure out who wants to kill her.

Challengers of the Unknown No. 37
April-May 1964
Cover: Prof. Elber felling Challengers by painting X’s on their portraits //Bob Brown
Story: “The Triple Terror of Mr. Dimension” (12 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Prof. Kurtz, a timeship captain (only appearance for both)
Villain: Mr. Dimension (first and only appearance)
Synopsis: A vagrant chances upon a dimensional weapon dropped from a timeship, becomes a super-villain named Mr. Dimension, and runs afoul of the Challengers.

Story: “The Last Days of the Challengers” (13 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (origin retold in flashback)
Villains: Prof. Elber (first appearance; dies in this story), a Prof. Elber robot, two robots (first appearance for all; all destroyed in this story)
Synopsis: The Challengers appear to be dying one by one as they try to stop two rampaging giant robots.

Challengers of the Unknown No. 38
June-July 1964
Cover: The Ooze vs. the Challengers //Bob Brown
Story: “The Menace the Challengers Made” (13 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villain: The Ooze (Killer Starke; first and only appearance)
Synopsis: The Challengers accidentally cause a criminal to be changed into The Ooze, a monster with the ability to absorb all solid matter.

Story: “Time Bomb on Holdout Island” (12 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Doctor Heller, Col. Takawa, and their soldiers (first and only appearance for all)
Synopsis: The Challengers find a secret army of neo-Fascists on a supposedly deserted island.

Challengers of the Unknown No. 39
August-September 1964
Cover: //Bob Brown
Story: “The Phantom of the Fair” (14 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Other Character: Madame Zaddum (last appearance in issue #35; last appearance)
Cameo appearances: The Sons of the Challengers, June Robbins (last appearance for all in issue #35; as characters in a crystal ball vision; last appearance for all), Stokie Johnson (first and only appearance)
Comment: This is the second and last Sons of the Challengers story.
Synopsis: The Challengers meet with Madame Zaddum again and see in her crystal ball a vision of themselves and the Sons of the Challengers in the future, fighting a villain who intends to reduce the older Challs to children.

Story: “Rocky, the Genius Challenger” (11 pages)
Editor: Murray Boltinoff
Writer:
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villain: Wizard Welles (first and only appearance)
Synopsis: A criminal scientist’s machine accidentally enlarges Rocky’s cranium and gives him super-genius intelligence--and an ego to match.

Challengers of the Unknown No. 40
October-November 1964
Cover: Multi-Man (in bee form) and giant bees vs. Challengers //Bob Brown
Story:   “The Super Powers of the Challengers” (12 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: A gang of crooks
Comment: Red Ryan gains an electrical suit, Ace Morgan gets a jet-pack, and Prof acquires a special diving suit in this story.  The new “powers” are not used in every story.
Synopsis: Three Challengers design mechanical devices to help them fight crime and put them to use fighting a gang of crooks who use super-machines of their own.

Story: “The Spy In Challenger Cave” (12 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villain: Multi-Man (between issues #34 / 42)
Comment: This story contains a diagram of Challenger Mountain.
Synopsis: Multi-Man smuggles a robot insect into Challenger Mountain and seeks to learn the secret of the Challengers’ “Project M-E”.

Challengers of the Unknown No. 41
December 1964 / January 1965
Cover: Rocky (in civvies) walking past Prof, Ace, and Red fighting the Quadruple Man //Bob Brown
Story: “The Challenger Who Quit” (18 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Dr. Burke (dies before this story begins), Dr. Hanford (only appearance)
Villains: The Quadruple Man, Fear (first appearance for both; both destroyed in this story)
Synopsis: Rocky fears recurring bouts of crushing headaches will decrease his efficiency with the Challengers, so he quits the team just as the others are facing the bizarre Quadruple Man.

Story: “Two Hours To Die”
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villain: The Cyclops (in flashback; cameo; first and only appearance)
Synopsis: Prof becomes stuck underwater with a bomb set to go off in two hours, and the other Challengers must rescue him.

Challengers of the Unknown No. 42
February-March 1965
Cover: Challengers vs. League of Challenger-Haters //Bob Brown
Story: “The League of Challenger-Haters” (13 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: The League of Challenger-Haters (Multi-Man (between issues #40 / 45), Drabny, Kra (both between issues #8 / 45), Volcano Man (between issues #32 / 45); first team appearance)
Synopsis: Four old enemies of the Challengers form the League of Challenger-Haters and plan to kill the Challengers one at a time by splitting them up.

Story: “The Secret of the Masked Challenger” (12 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: The Mandroid (first appearance; destroyed in this story) and his master (first and only appearance)
Synopsis: A strange gem gives Red laser-like vision and forces him to mask his face in bandages while a criminal scientist runs rampant with his massive Mandroid.

Challengers of the Unknown No. 43
April-May 1965
Cover: Challengers and mutant monster in museum with giant scorpion and dinosaur //Bob Brown
Story: “Four Against Monstro” (12 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (next appear in second story of next issue)
Villain: Monstro (first and only appearance; possibly dies in this story)
Comment: Rocky comments that he “wanted to ask that guy in the future if the Mets win a pennant!  And the way we live on borrowed time, we might not be around long enough to find out if they do!”  Since the Mets won the World Series in 1968, we can be assured that Rocky was.
Synopsis: Men from 2265 come back three centuries to recruit the Challengers to help them find a way to destroy a monster who came to Earth in the heroes’ time.

Story: “The Haunted Island” (13 pages)
Editor: Murray Boltinoff
Writer: Bill Finger
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (last chronological appearance in second story of issue #47; all get new uniforms in this story)
Villains: Five mutants (first appearance for all; all die in this story)
Comments: The Challengers’ old purple uniforms are replaced by yellow-and-red ones in this story.
Synopsis: The Challengers are lured to an island by five mutants who wish to keep them on permanent exhibit in their museum of things that should be extinct, yet still survive.

Challengers of the Unknown No. 45
June-July 1965
Cover: The Eye inducing Rocky to pull Ace, Red, and Prof into chasm containing a giant hand //Bob Brown
Story: “The Curse of the Evil Eye” (13 pages)
Editor: Murray Boltinoff
Writer: Bill Finger
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Origin: Ace Morgan (details; in flashback)
Supporting Characters: Anthony Dragio and other future members of the Challenger Corps (first appearance for all; all next appear in issue #49)
Intro: Count Mario Dragio (dies in this story), Count Lorenzo Dragio, an alchemist (both in flashback; only appearance for both)
Villains: The Eye (first and only appearance), Dragio (first appearance; dies in this story)
Comment: In this story, it is revealed that Ace was a fighter pilot in World War II.
Synopsis: The Challengers have to stop an alchemist’s giant death-dealing Eye from murdering all the surviving members of the Dragio family.

Story: “Ace--the Challenger Who Went Bad” (12 pages)
Editor: Murray Boltinoff
Writer: Dave Wood
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (last appearance in first story of last issue; next appear in second story of issue #47)
Villains: Gas Master (Dr. Marn), Zaab (first and only appearance for both)
Comment: The Challengers wear their old uniforms in this flashback story, so we have arbitrarily placed it just before the story in which they gain their new uniforms.
Synopsis: The Challengers go up against the Gas Master, one of whose weapons causes Ace to become a turncoat.

Challengers of the Unknown No. 45
August-September 1965
Cover: Multi-Woman, Multi-Man, Volcano Man, Drabny, and Kra vs. Challengers //Bob Brown
Story: “The Queen of the Challenger-Haters” (part 1; 8 pages)
 Part 2: “The Deadly Allies” (10 pages)
 Part 3: “Prisoners of the Earth” (6 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Jim and his partner (only appearance for both)
Villains: The League of Challenger-Haters (Multi-Man, Volcano Man, Kra, Drabny (all between issues #42 / 48), Multi-Woman (between issues #34 / 48; joins the League of Challenger-Haters in this story))
Synopsis: Multi-Woman joins the League of Challenger-Haters and helps them implement a plan to destroy the Challengers by deceit.

Challengers of the Unknown No. 46
October-November 1965
Cvoer: Gargoyle using Ace as bell-clapper while Rocky, Red, and Prof look on; “mystery Challenger” vignette //Bob Brown
Story: “The Strange Schemes of the Gargoyle” (12 pages)
Editor: Murray Boltinoff
Writer: Bill Finger
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: Laura (only appearance)
Villains: The Gargoyle (“Gary Doyle”) and his gang (including Smiley; first appearance for all)
Comment: Story continues in part in the second story of this issue.
Synopsis: A roof-crawling criminal called the Gargoyle falls in love with a blind girl, whose sight he hopes to restore by paying for an operation, but must contend with the Challengers.

Story: “The Best Challenger Wins” (12 pages)
Editor: Murray Boltinoff
Writer: Bill Finger
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: June Robbins (last appearance in issue #35; next appears in SUPER-TEAM FAMILY #8)
Villains: The Gargoyle and his gang (last appearance for all)
Comment: Ace Morgan becomes the Challengers’ leader in this story.
Synopsis: The Challengers go after the Gargoyle in the villain’s mountain hideout, each armed with a seemingly useless “weapon”.

Challengers of the Unknown No. 47
December 1965 / January 1966
Cover: Challengers vs. the Sponge Man //Bob Brown
Story: “The Sinister Sponge” (11 pages)
Editor: Murray Boltinoff
Writer: Bill Finger
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Intro: The Sponge Man (Miklos; first appearance; next appears in issue #51)
Villains: Stacy (first and only appearance), Lisa (alias Number 8 of Scorpio; named in her next appearance, in issue #51)
Synopsis: A diver is turned into a human sponge by a strange artifact and threatens to soak up the Earth’s water supply unless the Challengers can stop him.

Story: “The Terrors of Mr. Tic-Tac-Toe” (13 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (last appearance in second story of issue #45; next appear in second story of issue #44)
Villains: Mr. Tic-Tac-Toe (Dr. Bradford), Herbert (first and only appearance for both)
Comment: Since the Challengers wear their old uniforms in this story, we have placed it before the second story in issue #47 in which they gain new uniforms.
Synopsis: A villain who uses traps with a tic-tac-toe motif snares the Challengers to try to gain a secret vial they are guarding.

Challengers of the Unknown No. 48
February-March 1966
Cover: Negative Man, Elasti-Girl, and Robotman carrying off Rocky, Red, and Ace //Bob Brown
Story: “Twilight of the Challengers” (part 1; 8 pages)
 Part 2: “Kingdom of Darkness” (8 pages)
 Part 3: “The Battle of the Female Titans” (8 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (next appear in DOOM PATROL #102)
GS: Doom Patrol (Chief, Elasti-Girl, Robotman, and Negative Man; between DOOM PATROL #101 / 102)
Villains: The League of Challenger-Haters (Drabny (last appearance in issue #45; dies in this story), Multi-Man, Multi-Woman, Kra, Drabny, Volcano Man; last appearance for all in issue #45; all next appear in DOOM PATROL #102)
Comment: Story continues in DOOM PATROL #102, in which the Challengers and the Doom Patrol finish their battle against the Challenger-Haters.
Synopsis: When the Challengers are at the point of death following a battle against the Challenger-Haters, they summon the Doom Patrol to attempt to save their lives.

Challengers of the Unknown No. 49
April-May 1966
Cover: Korba and Iron Emperor vs. Challengers //Bob Brown
Story: “The Tyrant Who Owned the World” (24 pages)
Editor: Murray Boltinoff
Writer: Bill Finger
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (last appearance in DOOM PATROL #102)
Supporting Characters: The Challenger Corps (including Anthony Dragio and Tom Kaloki (first appearance); last appearance in issue #45; named in this story; last appearance for all)
Villains: Korba, the Iron Emperor, the Totem (first and only appearance for all)
Synopsis: The Challengers are aided by a group of civilian allies who call themselves the Challenger Corps when they confront Korba, a “man without a country” who enslaves people to construct his own “world” on an island.

Challengers of the Unknown No. 50
June-July 1966
Cover: Rocky releasing Ace (who turns into monster) from cell, as imprisoned Prof and Red look on; Villo vignette //Bob Brown
Story: “Final Hour For the Challengers” (part 1; 6 pages)
 Part 2 (8 pages)
 Part 3: “Villo’s Villa of Evil” (10 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Villo, Brainex (first appearance for both; both next appear in issue #52), a gang of crooks (first and only appearance)
Comment: Challenger Mountain is destroyed in this story.
Synopsis: Villo, the “world’s wickedest villain”, is hired by a criminal consortium to destroy the Challengers, and turns Ace into a monster to accomplish the job.

Challengers of the Unknown No. 51
August-September 1966
Cover: Sea Devils, Ace, Rocky, and Red vs. Sponge Man //Bob Brown
Story: “Smash the Sponge Man--Or Die” (24 pages)
Editor: Murray Boltinoff
Writer: Bill Finger
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
GS: The Sea Devils (Dane Dorrance, Biff Bailey, Nicky Walton, and Judy Walton; between SEA DEVILS #? / ?), Neptimus (between SEA DEVILS #? / ?)
Intro: Admiral Hutton (only appearance)
Other Characters: The Sponge Man (last appearance in issue #47; dies in this story)
Villains: Scorpio (a criminal organization; including Number 1, Number 2, and Number 3; first and only appearance), Lisa (Number 8; last appearance in issue #47; last appearance)
Synopsis: The Sponge Man goes on a rampage against the surface world when bombs kill sea life, and the Challengers and Sea Devils unite to stop him.

Challengers of the Unknown No. 52
October-November 1966
Cover: A Brutal vs. the Challengers //Bob Brown
Story: “Two Are Dead--Two To Go” (23 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Letterer: Gaspar Saladino
Feature Characters: Challengers of the Unknown
Origin: Ace Morgan, Prof Haley, Red Ryan (details revealed)
Villains: Villo, Brainex (both between issues #50 / 54), the Brutals (first and only appearance)
Synopsis: Villo and Brainex plan to destroy the Challengers individually by probing into their pasts.

Challengers of the Unknown No. 53
December 1966 / January 1967
Cover: Dimension Man vs. Challengers; Iron Dictator vignette //Bob Brown
Story: “Who Is the Traitor Among Us?”  (24 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Letterer: Gaspar Saladino
Feature Characters: Challengers of the Unknown
Intro: Scientist-X (as a voice and a recorded image, and in flashback; only appearance)
Villains: Dimension-Man, the Iron Dictator (Adolf), neo-Nazis (first and only appearance for all)
Comment: The Challengers gain a new headquarters and new devices designed by Scientist-X in this story.
Synopsis: The Challengers are given clues to the whereabouts of fantastic devices bequeathed to them by an alien scientist, but Dimension-Man and the Iron Dictator intend to snatch the inventions from the heroes once they are found and use them to conquer Earth.

Challengers of the Unknown No. 54
February-March 1967
Cover: //Bob Brown
Story: “War of the Sub-Humans” (24 pages)
Editor: Murray Boltinoff
Writer: France Herron
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Villo, Brainex (last appearance for both in issue #52)

Challengers of the Unknown No. 55
April-May 1967
Cover: Rocky, Prof, Ace, and Red’s ghost at Red’s gravesite //Bob Brown
Story: “Taps For Red” (24 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (Red Ryan apparently dies in this story, but returns as Seekeenakee in issue #59; next chronological appearance in flashback in second story of issue #61; Challengers are Rocky, Prof, and Ace until issue #60)
Villains: The League of Challenger-Haters (Villo, Brainex (both join in this story; last appearance for both), Multi-Woman (last appearance in DOOM PATROL #102; last appearance), Multi-Man, Kra, and Volcano Man; last appearance for all in DOOM PATROL #102; all next chronologically appear in flashback in second story of issue #61), Tino Manarry (Martin Ryan; first appearance)
Synopsis: To stop the Challenger-Haters from destroying the Earth with a massive volcanic eruption, Red Ryan triggers a neutralizing device and apparently loses his life.

Challengers of the Unknown No. 56
June-July 1967
Cover: Taputoca vs. Challengers //Bob Brown
Story: “License To Kill” (23 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (Rocky Davis, Prof Haley, and Ace Morgan through issue #59)
Origin: Ace Morgan (details)
Cameo: Red Ryan (in a picture)
Intro: Princess Diza (only appearance), the Colonel (Tino’s manager; first appearance; named in issue #71)
Villains: Tino Manarry, Taputoca (first and only appearance)
Synopsis: The Challengers, in Mexico to find an antidote for a dying scientist, run afoul of a hidden Aztec tribe, while Tino Manarry goes after the Challs with murder in mind.

Challengers of the Unknown No. 57
August-September 1967
Cover: Tino Manarry and Power Man vs. Ace, Rocky, and Prof //Gil Kane
Story: “The Kook and the Kilowatt Killer” (24 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Cameo appearance: Red Ryan (in flashback)
Other character: The Colonel (next appears in issue #71)
Villains: Tino Manarry (no longer a villain after this story), Power Man (first and only appearance)
Synopsis: Tino Manarry rescues an energy-absorbing villain, Power Man, from the police in order to send him against the Challengers.

Challengers of the Unknown No. 58
October-November 1967
Cover: Neutro changing Rocky to carbon as Ace and Prof look on //Bob Brown
Story: “Live Till Tomorrow” (23 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: Tino Manarry
Cameo appearances: Multi-Man, Villo, Kra
Villain: Neutro (Starrett; first and only appearance)
Synopsis: The Challengers face Neutro, an element-transmuting villain.

Challengers of the Unknown No. 59
December 1967 / January 1968
Cover: Rocky, Prof, and Ace being swallowed by Seekeenakee //Gil Kane
Story: “Seekeenakee, the Petrified Giant” (23 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Supporting Character: Tino Manarry
Intro: Col. Brackenshaw (dies in this story), Dr. Newberry (only appearance)
Villains: Seekeenakee (Red Ryan; revealed in issue #?; last chronological appearance in flashback in issue #?), Venuka, Prof. Danton, Medina, Harry Koone  (first and only appearance for all)
Synopsis: The Challengers battle an incarnate stone “god”, Seekeenakee, whose worshippers intend to control the world.

Challengers of the Unknown No. 60
February-March 1968
Cover: Ace, Prof, and Rocky watching Seekeenakee transform himself into Red Ryan //Bob Brown
Story: “The Thing That Could Not Die” (24 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Letterer: Gaspar Saladino
Feature Characters: Challengers of the Unknown (rejoined by Red Ryan in this story)
Supporting Character: Tino Manarry (next appears in issue #63)
Intro: Morton, Miss Pavelli (only appearance for both)
Villains: Seekeenakee (revealed as and transformed back to Red Ryan in this story; rejoins the Challengers), Multi-Man (last chronological appearance in flashback in second story of issue #61; next appears in SUPER-TEAM FAMILY #10), Kra, Volcano Man (last chronological appearance for both in flashback in second story of issue #61; both next appear in SUPER-TEAM FAMILY #10; latter three appear as the League of Challenger-Haters)
Synopsis: The Challengers learn the true identity of Seekeenakee and seek to change him back to his normal form before it is too late.

Challengers of the Unknown No. 61
April-May 1968
Cover: Chang directing two robot hands to grasp the Challengers //Bob Brown
Story: “The Robot Hounds of Chang” (16 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Villains: Chang (first appearance; dies in this story) and his robots (first and only appearance for all)
Comment: Story continues in part in second story of this issue.
Synopsis: The Challengers track down an Asian mastermind, Chang, to his island lair, and end up being human prey chased by Chang’s robots.

Story: “The Chall Without a Memory” (8 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (Red Ryan also appears in flashback; last chronological appearance before flashback in issue #55; next chronological appearance after flashback in flashback of second story in next issue)
Villains: Hakim, Ringo (first and only appearance for both), Multi-Man, Kra, Volcano Man (the League of Challenger-Haters; chronologically between issues #55 / 60)
Synopsis: Red Ryan tells the Challengers of how he was made amnesiac by the explosion of the bomb that foiled Multi-Man’s planned destruction of Earth, how he was duped by Multi-Man into acquiring the “liquid light” that triggers the villain’s transformations, and how, upon drinking it himself to keep it away from Multi-Man, he was transformed into a villain with Multi-Man’s body-changing powers.

Challengers of the Unknown No. 62
June-July 1968
Cover: Hordred, Count Karnak, and Madoga vs. Challengers //Bob Brown
Story: “The Legion of the Weird” (16 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown
Origin: Rocky Davis (details)
Intro: Granny Stopes (only appearance; Rocky’s maternal grandmother)
Villains: The Legion of the Weird (Vera Wycker, Count Karnak, Madoga, Hordred, Kaftu; first appearance for all)
Synopsis: A sorceress, in order to join the Legion of the Weird, attempts to murder Ace Morgan with a voodoo doll.

Story: “Me--the Walking Nightmare” (8 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Artist: Bob Brown
Feature Characters: Challengers of the Unknown (Red Ryan also appears in flashback, chronologically between flashback in second story of last issue and issue #59; first appears as Seekeenakee in this issue)
Cameo appearances: Multi-Man, Kra (in flashback)
Intro: Tiana (dies in this story; in flashback)
Villain: Herbert Pike (in flashback; first and only appearance)
Synopsis: Red Ryan continues his narrative of his amnesiac time, revealing how he fell in with a crooked promoter and first became Seekeenakee.

Challengers of the Unknown No. 63
August-September 1968
Cover: Tukamenon holding gem with Tino Manarry’s image in it as Red and Rocky approach //Bob Brown
Story: “None Shall Escape the Walking Evil” (24 pages)
Editor: Murray Boltinoff
Writer: Arnold Drake
Penciller: Bob Brown
Inker: Jack Abel
Feature Characters: Challengers of the Unknown
Supporting Character: Tino Manarry (between issues #60 / 66)
Villains: Tukamenon (first appearance; next appears in issue #66), Legion of the Weird (next appear in issue #66)
Comment: In this story, Tino Manarry is blinded, and Red Ryan donates an eye to him, but gains the power to see what Tino sees.
Synopsis: The Legion of the Weird sets an ancient mummy against the Challengers.

Challengers of the Unknown No. 64
October-November 1968
Cover: Challengers walking towards a gallows //Joe Kubert (signed)
Story: “Invitation To a Hanging” (12 pages)
Editor: Murray Boltinoff
Writer: Robert Kanigher
Artist: Jack Sparling
Feature Characters: Challengers of the Unknown
Intro: Judge Bentley, John Evans (both die in this story)
Villains: Doc Hemlock, Wolf Dengon, Shark Powell, Snake Saunders (first appearance for all; all die in this story), android doubles of Wolf Dengon, Shark Powell, and Snake Saunders (first appearance for all; all destroyed in this story)
Synopsis: The Challengers must face four foes seemingly risen from the grave, and out for revenge.

Challengers of the Unknown No. 65
December 1968 / January 1969
Cover: Giant alien reaching for the Challengers //Jack Sparling
Story: “The Devil’s Circus” (12 pages)
Editor: Murray Boltinoff
Writer: Robert Kanigher
Artist: Jack Sparling
Feature Characters: Challengers of the Unknown
Villain: A giant alien (first appearance; dies in this story)
Synopsis: An alien giant captures the Challengers and makes them perform in his “devil’s circus”.

Challengers of the Unknown No. 66
February-March 1969
Cover: Challengers of the Unknown, Tino Manarry, Tukamenon, Vera Wycker, Madoga //Joe Kubert
Story: “Rendezvous With Revenge” (23 pages)
Editor: Murray Boltinoff
Writer: Mike Friedrich
Artist: Jack Sparling
Feature Characters: Challengers of the Unknown
Supporting Character: Tino Manarry (last appearance in issue #63)
Villains: Legion of the Weird (Kaftu dies in this story; last appearance for all in issue #63; last appearance), Tukamenon (last appearance in issue #63; dies in this story), Om (first and only appearance)
Comment: Red loses the power to see what Tino sees in this story.
Synopsis: The Challengers stage a rescue mission to try to wrest Tino Manarry from the Legion of the Weird.

Challengers of the Unknown No. 67
April-May 1969
Cover: Red Ryan, Tino Manarry, Prof Haley, and image of Tino Manarry menaced by dream-creatures //Neal Adams
Story: “The Dream Killers” (14 pages)
Editor: Murray Boltinoff
Writer: Robert Kanigher
Artist: Jack Sparling
Feature Characters: Challengers of the Unknown
Supporting Character: Tino Manarry (next appears in issue #71)
Villain: An alien brain (first appearance; dies in this story)
Synopsis: Tino and people all over the city are menaced by killers in their dreams, so the Challengers enter the dream-world in order to fight the killers.

Story: “Ace: the Beast In the Bomb” (10 pages)
Editor: Murray Boltinoff
Writer: Robert Kanigher
Artist: Jack Sparling
Feature Characters: Challengers of the Unknown
Intro: Dr. Stevens (only appearance)
Villain: An unnamed villain (first appearance; dies in this story)
Synopsis: A villain clamps an iron mask containing a bomb to Ace’s head, and the other Challengers must find a way of deactivating it.

Challengers of the Unknown No. 68
June-July 1969
Cover: Prof freeing monster as Rocky, Red, and Ace approach //Neal Adams
Story: “One of Us Is a Madman” (24 pages)
Editor: Murray Boltinoff
Writer: Denny O’Neil
Penciller: Jack Sparling
Inker: Vince Colletta
Feature Characters: Challengers of the Unknown
GA: Richard Nixon (of Earth-One)
Villains: Dr. Fillmore (first and only appearance), the “computer monster” (first appearance; destroyed in this story)
Comment: Prof becomes corrupted by a spiritual evil in this story.
Synopsis: The Challengers must battle a monster spawned from a living computer and a scientist’s brain.

Challengers of the Unknown No. 69
August-September 1969
Cover: Challengers and shadow of Corinna Stark //Joe Kubert (signed)
Story: “The Secret of Skull Mountain” (23 pages)
Editor: Murray Boltinoff
Writer: Denny O’Neil
Artist: Jack Sparling
Feature Characters: Challengers of the Unknown
Supporting Character: Corinna Stark (first appearance)
Cameo appearance: Eli Swade (in a photograph; only appearance; dies before this story begins)
Villain: Algernon Stark (first appearance), an android (first appearance; destroyed in this story)
Comments: Prof is wounded in this story.  He remains an inactive member until issue #?, but appears in all stories.
 This story continues in the next issue.
Synopsis: The Challengers investigate a murder apparently committed by a dead man.

Challengers of the Unknown No. 70
October-November 1969
Cover: Chu, Corinna Stark, Red, Ace, and Rocky //Neal Adams
Story: “A Scream of Yesterdays” (23 pages)
Editor: Murray Boltinoff
Writer: Denny O’Neil
Artist: Jack Sparling
Feature Characters: Challengers of the Unknown (get new uniforms in this story; Corinna Stark joins the team; Prof remains inactive)
Villains: Algernon Stark (dies in this story), Chu (a Toggan), the Slaves of Chu (first appearance for all)
Comment: Story continues in next issue.
Synopsis: The Challengers find themselves in the clutches of an alien being who kills Corinna’s father and plans to do the same to them.

Challengers of the Unknown No. 71
December 1969 / January 1970
Cover: Ace, Corinna Stark, Rocky, and Red chained to posts before children and witch //Nick Cardy
Story: “When Evil Calls” (23 pages)
Editor: Murray Boltinoff
Writer: Denny O’Neil
Penciller: Jack Sparling
Inker: Frank Giacoia
Feature Characters: Challengers of the Unknown (including Corinna Stark; Prof still inactive)
Supporting Character: Tino Manarry (last appearance in issue #67; last appearance)
Other Character: The Colonel (last appearance in issue #57; last appearance)
Villains: Chu (dies in this story), Slaves of Chu (last appearance), Joshua Slade (first appearance; dies in this story), Granny Dark (first and only appearance)
Comment: Red Ryan gains two working eyes through a transplant in this story.
Synopsis: The Challengers are captured by the Slaves of Chu, but Tino Manarry leads an effort to rescue them.

Challengers of the Unknown No. 72
February-March 1970
Cover: Rocky, Ace, Red, and Corinna Stark with diseased cat //Neal Adams
Story: “A Plague of Darkness” (23 pages)
Editor: Murray Boltinoff
Writer: Denny O’Neil
Penciller: Dick Dillin
Inker: Frank Giacoia
Feature Characters: Challengers of the Unknown (including Corinna Stark)
Origin: Red Ryan (details)
Intro: Alfie Eisen, Dr. Harris, Ken Gilmore (only appearance for all)
Villain: Mr. Murlin (first and only appearance)
Synopsis: An alchemist’s potion releases a plague that turns ordinary people into violent zombies.

Challengers of the Unknown No. 73
April-May 1970
Cover: Ace, Rocky, Prof, Corinna Stark, and Machu in seance //Nick Cardy
Story: “The Curse of the Killer Time Forgot” (23 pages)
Editor: Murray Boltinoff
Writer: Denny O’Neil
Artist: George Tuska
Feature Characters: Challengers of the Unknown (including Corinna Stark)
Intro: An astronaut (dies in this story)
Villains: Machu (first and only appearance), Major Cheever (first appearance; dies in this story)
Synopsis: The Challengers investigate the murder of an astronaut in space.

Challengers of the Unknown No. 74
June-July 1970
Cover:  Neal Adams
Story: “To Call a Deadman"  (23 pages)
Editor:  Murray Boltinoff
Writer:  Denny O'Neil
Artists:  George Tuska (pages 1-16)
   Neal Adams (pages 17-23)
Feature Characters:  Challengers of the Unknown (including Corrina Stark)
GS:  Deadman (last seen in Aquaman #52; next appears in Justice League of America #94),
Jonny Double (last seen in Showcase #78; next appears in ADVENTURE COMICS #418)
Supporting Character:  Vashnu (between in Brave and the Bold #86 / 104)
Intro: Dr. McJames and his daughter (only appearance for both)
Villains:  Seth Gross (first and only appearance; technically dies in this story), Nodo (first and only appearance)
Synopsis:  Seth Gross, a wicked magician, befriends Vashnu, learns the secret of astral projection, and steals from him a mystic box with the power to trap a soul.  He goes into ghost-form and uses the box on the daughter of scientist McJames, forcing him to attempt jewel robberies in return for the soul of the little girl, who will remain in suspended animation for some time.  Jonny Double and the Challengers of the Unknown become involved in the case, but it is Deadman who actually fights Gross, inhabits his spirit-form in a particularly painful process, and restores the little girl's soul to her body in time.  At that, Deadman exits Gross's ectoplasmic form, with Gross driven insane by the experience and unable to return to his body.

Challengers of the Unknown No. 75
August-September 1970
Cover: Challengers vs. Ultivac’s hand; Ace Morgan vignette //George Tuska and Jack Kirby / Marvin Stein
Comment: Main vignette on cover reprinted from page 1 of “Ultivac Is Loose”; Ace Morgan vignette by George Tuska.
Story: [untitled; framing sequence] (1 page)
Editor: Murray Boltinoff
Writer: Denny O’Neil
Artist: George Tuska
Feature Characters: Challengers of the Unknown (including Corinna Stark (her last appearance; Prof, Ace, Rocky, and Red next appear in SUPER-TEAM FAMILY #8)
Comment: The rest of this issue features a reprint of “Ultivac Is Loose” (from SHOWCASE #7).  Issues #76-81 are all reprints.  The next original Challengers story appears in SUPER-TEAM FAMILY #8.
Synopsis: On a rainy night, the Challengers tell Corinna Stark of their battle against Ultivac.

Super-Team Family No. 8
December 1976 / January 1977
Cover: Challengers vs. Tyrannosaurus //Rich Buckler / Jack Abel (signed)
Story: “The Devil’s Paradise” (17 pages)
Editor: Tony Isabella
Writer: Steve Skeates
Penciller: James Sherman
Inker: Jack Abel
Letterer: Milt Snapinn
Colorist: Liz Berube
Feature Characters: Challengers of the Unknown (Ace, Rocky, Prof, and Red; last appearance for all in CHALLENGERS OF THE UNKNOWN #75; origin retold in flashback)
Supporting Character: June Robbins (last appearance in CHALLENGERS OF THE UNKNOWN #46; gets a costume and becomes the de facto fifth Challenger in this story; next appears in issue #10)
Other characters: President Gerald Ford, Henry Kissinger (both of Earth-One)
Villains: The Tribunal and other Bermuda Triangle inhabitants (first and only appearance for all)
Synopsis: Henry Kissinger is lost in the Bermuda Triangle on a diplomatic mission, and the Challengers of the Unknown have to rescue him from an island filled with dinosaurs and time-lost humans.

Super-Team Family No. 9
February-March 1977
Cover: Challengers vs. flaming man  //Rich Buckler / Jack Abel (signed)
Story: “To Doomsday and Beyond” (17 pages)
Editor: Denny O’Neil
Writer: Steve Skeates
Penciller: Jim Sherman
Inker: Jack Abel
Feature Characters: Challengers of the Unknown
Intro: Three members of an ancient civilization (all die in this story)
Villain: Dr. Chrislow (first and only appearance)
Synopsis: The Challengers seek to destroy the bomb a mad scientist has placed in a volcano, but discover the last three members of an ancient super-scientific civilization within the volcano’s depths.

Super-Team Family No. 10
April-May 1977
Cover: Challengers of the Unknown and June Robbins vs. Multi-Man  //Rich Buckler / Jack Abel (signed)
Story: “Multi-Man Rules the World” (20 pages)
Editor: Joe Orlando
Writer: Steve Skeates
Penciller: Jim Sherman
Inker: Jack Abel
Feature Characters: Challengers of the Unknown (next appear in CHALLENGERS OF THE UNKNOWN #81)
Supporting Characters: June Robbins (last appearance in issue #8; next appears in CHALLENGERS OF THE UNKNOWN #81),  F. Gaylord Clayburn III (between CHALLENGERS OF THE UNKNOWN #30 / 81)
Villains: Multi-Man (between CHALLENGERS OF THE UNKNOWN #60 / 81) and his gang (first and only appearance), Kra, Volcano Man (last appearance for both in CHALLENGERS OF THE UNKNOWN #60; last appearance for both)
Comment: Story continues in CHALLENGERS OF THE UNKNOWN #81.
Synopsis: Multi-Man devises a method of becoming immaterial at will, and threatens to destroy cities until he is acknowledged as king of the world, but the Challengers oppose him again.

Challengers of the Unknown No. 81
June-July 1977
Cover: Challengers and June Robbins standing over fallen Multi-Man  //Mike Nasser / Neal Adams (signed)
Story: “Multi-Man’s Master Plan” (17 pages)
Editor: Jack C. Harris
Writer: Gerry Conway
Penciller: Mike Nasser
Inker: Bob Wiacek
Feature Characters: Challengers of the Unknown (last appearance in SUPER-TEAM FAMILY #10)
Supporting Characters: June Robbins, F. Gaylord Clayburn III (last appearance for both in SUPER-TEAM FAMILY #10)
Intro: Susan Charness
Villains: Multi-Man (last appearance in SUPER-TEAM FAMILY #10; next appears in issue #84), Heathcliff Monroe, M’nagalah and his cultists (last appearance for all in SWAMP THING (first series) #8)
Comment: Story continues from SUPER-TEAM FAMILY #10 and continues in next issue.
Synopsis: With Prof dying of a strange ailment, the Challengers of the Unknown continue their battle against Multi-Man.

Challengers of the Unknown No. 82
August-September 1977
Cover: Challengers of the Unknown and June Robbins vs. M’nagaleh //Mike Nasser / Joe Rubinstein (signed)
Story: “The Lurker Below” (chapter 1; 4 pages)
 Chapter 2: “Legacy of the Damned” (5 pages)
 Chapter 3: “The Soul Predator” (5 pages)
 Chapter 4: “The Lurker Rises” (4 pages)
Editor: Jack C. Harris
Writer: Gerry Conway
Penciller: Mike Nasser
Inkers: Joe Rubinstein, Berni Wrightson (pg. 7, panel 1 only)
Feature Characters: Challengers of the Unknown
Cameo appearance: Swamp Thing (origin retold in flashback)
Supporting Characters: June Robbins (counted as a Challenger in this and succeeding issues), F. Gaylord Clayburn III
Villains: Heathcliff Monroe, M’nagaleh cultists
Comments: A caption on page 3, panel 1, asserts that Ace Morgan was an astronaut and set foot on the moon, a claim that is probably untrue.
 The Challengers get new uniforms in this story, and June is probably accepted as the fifth Challenger.
 Story continues in next issue.
Synopsis: The Challengers go to Dr. Heathcliff Monroe seeking a cure for Prof, only to find that Monroe is a worshipper of the evil entity M’nagaleh, to whom he intends to sacrifice Rocky Davis.

Challengers of the Unknown No. 83
October-November 1977
Cover: Ace, Rocky, Red, June Robbins, and Swamp Thing vs. M’nagaleh //Rich Buckler / Joe Rubinstein (signed)
Story: “Seven Doorways To Destiny” (chapter 1; 2 pages)
 Chapter 2: “Savior From the Swamp?”  (3 pages)
 Chapter 3: “The Gods Crawl Closer” (5 pages)
 Chapter 4: “All Monsters Good and Evil” (7 pages)
Editor: Jack C. Harris
Writer: Gerry Conway
Penciller: Keith Giffen
Inker: John Celardo
Colorist: Jerry Serpe
Feature Characters: Challengers of the Unknown (including June Robbins)
GS: Swamp Thing (last appearance, as Alec Holland, in SWAMP THING (first series) #24; reverts to Swamp Thing form in this story)
Supporting Characters:  F. Gaylord Clayburn III, Ruth Monroe (last appearance in SWAMP THING (first series) #24; last appearance)
Villains: M’nagaleh, M’nagaleh cultists, Heathcliff Monroe (last appearance for all)
Comment: Story continues in next issue.
Synopsis: Gaylord Clayburn enlists the help of Dr. Alec Holland as Heathcliff Monroe, holding Prof’s life at stake, blackmails the other Challengers into casting a spell that will enable M’nagaleh to manifest on Earth.

Challengers of the Unknown No. 84
December 1977 / January 1978
Cover: Swamp Thing, Rocky, Red, Deadman, and Prof  //Rich Buckler / Joe Rubinstein (signed)
Story: “To Save a Monster” (chapter 1; 7 pages)
 Chapter 2: “When Deadmen Walk” (10 pages)
Editor: Jack C. Harris
Writer: Gerry Conway
Penciller: Keith Giffen
Inker: John Celardo
Colorist: Jerry Serpe
Feature Characters: Challengers of the Unknown (June Robbins confirmed as “honorary member” in this story; all but June next appear in SHOWCASE #100)
GS: Swamp Thing (origin retold in flashback), Deadman (last appearance in DC SUPER-STARS #18; origin retold in flashback)
Supporting Characters:  F. Gaylord Clayburn III (mistakenly called Dustin Clayburne in this story; last appearance), Rama Kushna (last appearance in DC SUPER-STARS #18; next appears in ADVENTURE COMICS #463)
Cameo appearance: Tiny (in flashback)
Villain: Multi-Man (last appearance in issue #81; last appearance)
Comment: Story continues from last issue.
 Shortly after this story the Challengers of the Unknown help the heroes of Earth fight an alien being in SHOWCASE #100.
Synopsis: Deadman helps Prof conquer his fungus disease, after which the Challengers trail the Swamp Thing, who is being mentally dominated by Multi-Man.

Challengers of the Unknown No. 85
February-March 1978
Cover: Giant hand menacuing Challengers and June Robbins //Rich Buckler / Jack Abel (signed)
Story: “The Creature From the End of Time” (chapter 1; 6 pages)
 Chapter 2: “Monsters and Men” (6 pages)
 Chapter 3: “Flight Into the Future” (5 pages)
Editor: Jack C. Harris
Writer: Gerry Conway
Penciler: Keith Giffen
Inker: John Celardo
Letterer: Milt Snapinn
Colorist: Jerry Serpe
Feature Characters: Challengers of the Unknown (including June Robbins; all but June last appear in SHOWCASE #100)
GS: Swamp Thing, Deadman, Rip Hunter (last appearance in SHOWCASE #100; origin retold in flashback)
Cameo appearances: Jeff Smith, Bonnie Baxter, Corky Baxter (in flashback)
Villains: Two monsters.
Comment: Story continues in next issue.
 Rip Hunter is said to have been gone for ten years in this story.
Synopsis: To combat menaces from cubes which appear in two cities, the Challengers, Swamp Thing, and Deadman travel to the year 12,000,000 A.D. in search of Rip Hunter.

Challengers of the Unknown No. 86
April-May 1978
Cover: Rip Hunter vs. Swamp Thing, Deadman, June Robbins, Rocky, and Ace //Rich Buckler / Frank Giacoia (signed)
Story: “The War At Time’s End”
 Chapter 1: “The Way It Began” (5 pages)
 Chapter 2: “If This Is Tomorrow, You Must Be Rip Hunter” (5 pages)
 Chapter 3: “Time Times Terror” (4 pages)
 Chapter 4: “A Pit By Any Other Name” (3 pages)
Editor: Jack C. Harris
Writer: Gerry Conway
Penciller: Keith Giffen
Inker: John Celardo
Colorist: Gene D’Angelo
Feature Characters: Challengers of the Unknown (including June Robbins)
GS: Swamp Thing, Deadman, Rip Hunter
Intro: Lucas Lawspeaker
Villains: The Sunset Lords, the Persuader (not to be confused with the Fatal Five villain; first appearance for all)
Comment: Story continues in next issue.
Synopsis: Deadman discovers that Rip Hunter’s mind has been taken over by the tyrant Sunset Lords of the future, and the ghost attempts to aid the Challengers and Swamp Thing in their battle against the villains.

Challengers of the Unknown No. 87
June-July 1978
Cover: Deadman, Swamp Thing, Rocky, June Robbins, and Ace near Time Sphere //Alex Saviuk / Dick Giordano (signed)
Story: “Twelve Million Years To Twilight”
 Chapter 1: “Assault on Sunset” (9 pages)
 Chapter 2: “Twilight’s Last Glimmer” (8 pages)
Editor: Jack C. Harris
Writers: Gerry Conway, Carla Conway
Penciller: Keith Giffen
Inker: John Celardo
Letterer: Ben Oda
Colorist: Jerry Serpe
Feature Characters: Challengers of the Unknown (next appearance of Ace, Rocky, Prof, and Red in WORLD’S FINEST COMICS #267;  June Robbins next appears in CRISIS ON INFINITE EARTHS #5)
GS: Swamp Thing (next appears in DC COMICS PRESENTS #8), Deadman (next appears in ADVENTURE COMICS #459), Rip Hunter (next appears in DC COMICS PRESENTS #37)
GA: Batman (last appearance in DC SPECIAL SERIES #11; next appears in SECRET SOCIETY OF SUPER-VILLAINS #12), Elongated Man (last appearance in DC SPECIAL SERIES #11; next appears in JUSTICE LEAGUE OF AMERICA #155), Green Lantern (last appearance in SHOWCASE #100; next appears in JUSTICE LEAGUE OF AMERICA #155), Lightray (last appearance in DC SPECIAL SERIES #10; next appears in NEW GODS #16), Demon (last appearance in BATMAN FAMILY #17; next appears in DETECTIVE COMICS #482)
Intro: Mica (only appearance)
Other Character: Lucas Lawspeaker (last appearance)
Villains: The Sunset Lords, the Persuader (last appearance for all)
Comments: This is the last issue of the original run of CHALLENGERS OF THE UNKNOWN.  A new mini-series with the same title began in 1991.
 A closing caption confirms that Deadman and Swamp Thing left the Challengers after this story.
 A diagram of Challenger Mountain appears on page 7.
Synopsis: While Red and Prof battle menaces in the present, Ace, Rocky, June, Deadman, and Swamp Thing fight the Sunset Lords to free the people of 12,000,000 A.D.

Challengers’ later appearances:

WORLD’S FINEST COMICS #267
DC COMICS PRESENTS #84
CRISIS ON INFINITE EARTHS #5, 8, 11, 12

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