Which Marvel villain is central to the storyline of X-Men '97 season 2?

Apocalypse is the Marvel villain central to the storyline of X-Men '97 season 2. The season follows the X-Men across time as they try to return to the 1990s and stop Apocalypse's plans.

The threat grows out of season 1's closing scenes, when the ancient mutant En Sabah Nur is revealed in Ancient Egypt. In Marvel continuity, En Sabah Nur is Apocalypse, an exceptionally powerful mutant who believes that only the strongest beings deserve to survive.

Season 2 explores Apocalypse in multiple eras. Some X-Men encounter his younger self in approximately 3000 B.C., while others face the consequences of his rule in the far future. His presence links the ancient, modern, and 3960 A.D. timelines.

Bastion and Mister Sinister are also important villains in X-Men '97, but their major conflicts belong chiefly to season 1. Mojo is a recurring Marvel antagonist, yet he is not the season's central threat.