Skullfire, whose real name is Timothy Fitzgerald, first appeared in X-Men 2099 #1 (October 1993), created by writer John Francis Moore and artist Ron Lim. Set in the Marvel 2099 universe, he is depicted as a mutant from Earth-928 who initially led a privileged life as a young urban professional. The traumatic manifestation of his powers resulted in an uncontrolled energy burst that destroyed his apartment and inadvertently caused the death of his girlfriend, leading to a period of isolation and wandering in the southwestern United States. Recruited by Cerebra, he joined a new incarnation of the X-Men assembled by Xi'an Chi Xan, marking his entry into the team as a founding member struggling with power control and personal guilt.

As a core member of the X-Men 2099, Fitzgerald adopted the codename Skullfire—though rarely used within the stories themselves—and distinguished himself with a skull-like face paint design. His abilities centered on absorbing ambient energy particles, metabolizing them, and releasing destructive blasts, which evolved to include enhanced energy manipulation. He formed romantic connections, notably with teammate Krystalin, and participated in key conflicts, including defenses against corporate threats and mutant oppressors. Skullfire contributed to the team's relocation to Halo City, where they established the Protectorate for security, demonstrating growing leadership and commitment to mutant protection amid the dystopian corporate-dominated world of 2099.

In later developments across the X-Men 2099 series and related titles like 2099: World of Tomorrow, Skullfire faced further trials, including temporary departures from the team to pursue leads on mutant sanctuaries and confrontations with figures like Zhao's unstable X-Men. His narrative explored themes of redemption and control, with instances of death and resurrection underscoring his resilience. Though the 2099 line concluded in the late 1990s, Skullfire remains a notable figure in Marvel's alternate future timeline, embodying the struggles of mutants in a cyberpunk era through his journey from instability to steadfast heroism.