The Morlocks are a group of mutants who have exiled themselves to the sewers of New York as they have deemed themselves too deformed to live on the surface.
The Morlocks first crossed paths with the X-Men when they kidnapped Cyclops and Jean Grey. This altercation lead to the mutant heroes discovering the sewer mutants and their leader Callisto having a duel with Storm for the leadership of the group. Storm won but when she could not persuade the Morlocks to come with her to Xavier's Institute, she left leaving Callisto in charge while she was absent. Later, the Morlock, Plague joined with the mutant terrorist, Apocalypse to become the Horseman, Pestilence. Lady Deathstrike and the Reavers later kidnapped the Morlocks and imprisoned them on an alien space ship. Whilst there, all the enrgies of the Morlocks were absorbed by an alien being but the X-Men and managed to rescue and restore their fellow mutants. The Morlocks later requested the aid of the X-Men when Leech became critically ill. Wolverine used his healing factor to cure the young mutant and Storm handed permanent leadership back to Callisto.