X-Factor #21

Published in 1987, X-Factor #21 serves as a pivotal entry in the series, written by Louise Simonson with artwork by Walt Simonson. This issue is historically significant for the introduction of Apocalypse, a character who would go on to become one of the most prominent antagonists in the X-Men mythos. The narrative focus at the time centered on the original five X-Men navigating their roles as mutant hunters while secretly operating as heroes, a premise that allowed for the introduction of darker, more existential threats like the immortal mutant Apocalypse.

The character design for Apocalypse was created by Jackson Guice, though Walt Simonson’s interior work refined the visual language that defined the villain's imposing silhouette and techno-organic aesthetic. The creative team aimed to establish a sense of ancient, unrelenting power that stood in stark contrast to the existing rogue's gallery. Upon release, the issue was well-received for its shift in tone and the expansion of the franchise's lore, marking a shift toward the complex, long-form storytelling that would characterize much of the late 1980s Marvel landscape.