Peter B. Gillis’ first work in the comics industry was as a freelance writer for Marvel Comics. His first published comics story was “Saturday Night Furor” in Captain America #224 (Aug. 1978). He then wrote various issues of Marvel Two-In-One, What If…?, and Super-Villain Team-Up from 1978 to 1980. The irregular publishing frequency of the final issues of Super-Villain Team-Up was due to a legal maneuver to prevent DC Comics from trademarking the term “supervillain”. Gillis then worked as an editor for the Florida-based publisher New Media Publishing; he left that position in June 1981.
He is best known for the digital comic Shatter (1985–1988) and First Comics’ Warp (1983–1985). Gillis co-created Strikeforce: Morituri (1986–1988) with artist Brent Anderson. Gillis wrote the entire runs of Micronauts: The New Voyages (1984–1986) and Strange Tales vol. 2 (1987–1988); other Marvel work included numerous issues of What If (1980–1984), The Defenders (1984–1986), The Eternals vol. 2 (1985–1986), Doctor Strange vol. 2 #76–81 (1986–1987) and Doctor Strange, Sorcerer Supreme #1–4 (1988–1989). The Defenders was Gillis’s first ongoing assignment; he recounted, “I had been working for a while at Marvel, and was constantly pumping for more work, and specifically a series of my own. So when I heard DeMatteis was leaving Defenders, I was in [editor] Carl Potts’ office like a shot, and I got the gig.”
His creations for other companies include Blaze Barlow and the Eternity Command and the Black Flame for First Comics; and Gammarauders, a tie-in to the Gamma World role-playing game, for DC Comics’ short-lived TSR Games line. He also wrote the science-fiction miniseries Tailgunner Jo with art by Tom Artis for DC.
Gillis returned to comics in 2010 when he wrote the six-issue comic adaptation of Peter S. Beagle’s The Last Unicorn for IDW Publishing.