Universe/Timeline:
Marvel Universe
The Four Horsemen of Apocalypse are the elite soldiers of En Sabah Nur, assembled to do his bidding and forcibly ensure the survival of the fittest. Apocalypse frequently brainwashes new servants to his cause, and forces them through enhancement procedures to ensure they are among the strong, and make them better suited to his needs. Several X-Men have been forced into his service in the past, beginning with Angel's transformation into Archangel.
Caliban is the only Horseman who has served in two different roles, first as Death and later as Pestilence.
