The Morlocks are a homeless colony of mutants who took up residence in the massive tunnels underneath New York. The Morlock Tunnels have extensive reach, existing underneath Manhattan and all the way to access points at the mansion in Westchester County. The Morlocks were founded by Callisto, Sunder, Masque and Caliban some time ago, after each individually fled from the surface world. The early days of the Morlocks are also tied to the Dark Beast, who carried out experiments on the early Morlocks after his arrival in our reality. The Dark Beast had been protege to Sinister in the Age of Apocalypse, and so when Mister Sinister in the main reality recognized some of his genetics work in the Morlocks, he ordered their extermination in the Mutant Massacre.

Callisto was the original leader of the Morlocks until Storm defeated her in combat in Uncanny X-Men #170. Storm's reign over the Morlocks continued uncontested through #215, when the Massacre scattered the survivors to Muir Island, X-Factor's compound, and elsewhere in the tunnels. Masque assumed control of the Morlocks in the absence of their former leaders in #254, mutilating many of the survivors with his powers. After his death in X-Force (1st series) #9, the remaining deranged Morlocks ran amok and apparently died in a suicide pact with Callisto and Mikhail Rasputin in Uncanny X-Men #293. Following the Storm limited series and Gene Nation storyline, it was learned that the Morlocks had actually transported to another dimension called the Hill, where they aged nearly two decades before returning to Earth.

Several splinter factions of Morlocks have appeared over the years, such as the Drain Dwellers of Power Pack (1st series) #12 and the Tunnelers of X-Factor (1st series) #11. After the transport to the Hill, other factions have appeared such as Carver's or Postman's.