Holocaust is a fictional character appearing in American comic books published by Marvel Comics. The character first appeared in X-Men Alpha, and was created by Scott Lobdell and Roger Cruz; however, a character with the same name and similar appearance was featured in Stryfe's Strike Files, two years before X-Men Alpha was released.

Apocalypse is a supervillain appearing in American comic books published by Marvel Comics. He is one of the world's first mutants, and was a principal villain for the original X-Factor team and later the X-Men and related spin-off teams. Created by writer Louise Simonson and artist Jackson Guice, Apocalypse first appeared in X-Factor #5. Apocalypse is one of the most powerful beings in the Marvel Universe where he is the husband of Genesis and the father of the original incarnation of the Horsemen of Apocalypse.