Roy William Thomas, Jr. (born November 22, 1940) is an American comic book writer and editor, who was Stan Lee's first successor as editor-in-chief of Marvel Comics.
 He is possibly best known for introducing the pulp magazine hero Conan the Barbarian to American comics, with a series that added to the storyline of Robert E. Howard's character and helped launch a sword and sorcery trend in comics.
 Thomas is also known for his championing of Golden Age comic-book heroes – particularly the 1940s superhero team the Justice Society of America – and for lengthy writing stints on Marvel's "X-Men" and "The Avengers", and DC Comics' "All-Star Squadron", among other titles.
Quality Comics was a comic book company from the Golden Age of Comic Books that sold many anthology comic books that starred superheroes, many of which were adopted by DC Comics when they purchased Quality Comics, and others were not, entering the public domain.
Major Malcolm Wheeler-Nicholson (January 4, 1890 or January 7, 1890 – 1965) was an American pulp magazine writer and entrepreneur who pioneered the American comic book, publishing the first such periodical consisting solely of original material rather than reprints of newspaper comic strips.
 Long after his departure from the comic book company he founded, Wheeler-Nicholson's National Allied Publications would evolve into DC Comics, one of the U.S.'s two largest comic book publishers along with rival Marvel Comics.
Innovation Publishing (also known as Innovation Books) was an American comic book company based in Wheeling, West Virginia.
 It was co-founded by David Campiti in 1988 after writing a business proposal and raising US$400,000 to finance its launch.
 Innovation became #4 in market share, below Marvel Comics, DC Comics, and Dark Horse Comics.
Gary Edson Arlington (October 7, 1938 – January 16, 2014) was an American retailer, artist, editor, and publisher, who became a key figure in the underground comix movement of the 1960s and 1970s.
 As owner of America's first comic book store, the San Francisco Comic Book Company, located in San Francisco's Mission District, Arlington's establishment became a focal point for the Bay Area's underground artists.
 He published comics under the name San Francisco Comic Book Company as well as Eric Fromm (not connected to the German critical theorist).
 Cartoonist Robert Crumb has noted, "Gary made a cultural contribution in San Francisco in the late '60s, through the '70s, '80s & '90s that was more significant than he realizes."
Captain Carrot is a funny animal superhero published by DC Comics.
 His first appearance was in a special insert in "The New Teen Titans" #16 (cover-dated Feb. 1982).
 He was created by Roy Thomas and Scott Shaw.
Swordquest is an unfinished series of video games produced by Atari, Inc. in the 1980s as part of a contest, consisting of three finished games and a planned but never released fourth game.
 Each of the games came with a comic book that explained the plot, as well as containing part of the solution to a major puzzle that had to be solved to win the contest, with a series of prizes on offer whose total value was $150,000.
 The series had its genesis as a possible sequel to Atari's groundbreaking 1979 title "Adventure", but it quickly developed a mythology and system of play that was unique.
 The comic books were produced by DC Comics, written by Roy Thomas and Gerry Conway, and drawn and inked by George Pérez and Dick Giordano.
 A special fan club offer was provided, allowing those who wanted the game, to also get a T-shirt and poster for each game.
Captain Carrot and His Amazing Zoo Crew!
 is a DC Comics comic book about a team of funny animal superheroes called the Zoo Crew.
 The characters first appeared in a special insert in "The New Teen Titans" #16 (February 1982), followed by a series published from 1982 to 1983.
 The Zoo Crew characters were created by Roy Thomas and Scott Shaw.
 Although the series, which was the last original funny animal property created by DC Comics, proved short-lived, it is still fondly remembered by many comic fans of its generation, and the characters appear occasionally in cameos in the mainstream DC Universe (this is made possible due to the existence of a "multiverse" in the DCU, which allows the Zoo Crew characters to exist on a parallel Earth).
"Crisis on Infinite Earths" is an American comic book crossover storyline published by DC Comics from 1985 to 1986, consisting of an eponymous 12-issue, limited series comic book and a number of tie-in books.
 It was produced by DC Comics to herald a simplification of its then 50-year-old narrative continuity.
 The series was written by Marv Wolfman and illustrated by George Pérez (pencils and layouts), Mike DeCarlo, Dick Giordano and Jerry Ordway (inking and embellishing).
 The series removed the multiverse concept from the fictional DC Universe, depicting the death of long-standing characters Supergirl and the Barry Allen incarnation of the Flash.
 Continuity in the DC Universe is divided into pre-Crisis and post-Crisis periods.
 Crisis is considered by many to be one of the most important and most influential comic book storylines of all time.
Arak is a fictional comic book character published by DC Comics.
 He first appeared in a special insert in "The Warlord" #48 (August 1981) and was created by Roy Thomas and Ernie Colón.
 Arak (Bright-Sky-After-Storm) is depicted very much as a Conan knock-off in early appearances.
 Later, after encountering the Moirai, who explain his destiny to him, he takes on a more Native American appearance, including leather-fringed pants and a Mohawk hairstyle.
 Unlike Conan (a character Roy Thomas also wrote during his tenure at Marvel Comics), who usually fought against H. P. Lovecraftian monsters and entities, Arak encounters figures and creatures from myth and legends, including Greek, Norse, Judeo-Christian, Muslim, Oriental, and others.

Question: After working for DC Comics, Roy Thomas then became editor-in-chief at which comic book company?
Answer: Marvel Comics