Real Name: Cain Marko
Affiliation: None
Origin: New York, NY
Powers: Superhuman strength, level ten invulnerability
Background: Little is known about the Juggernaut's past, save for the fact that his father married Charles Xavier's mother after Xavier's father's death. When he grew up, Cain used secret mystic energies to acquire great power, turning him into the unstoppable Juggernaut. In their first encounter, Charles managed to subdue the behemoth through a mental attack, and developed a stasis tank which keeps Juggernaut completely paralyzed.

Years later, the mutant shape-shifter Mystique awakened the giant in an attempt to gain control of Xavier's mutant-tracking computer, Cerebro. Juggernaut turned on her, preferring to exact his vengeance on his step-brother, and trudged to Xavier's School for Gifted Youngsters, forcing a union between Mystique's Brotherhood of Mutants and Xavier's X-Men in order to stop the giant. Using a lot of teamwork, the mutants finally open all the latches to Cain's psi-blocking helmet, allowing Toad to yank it off. Professor X was then able to telepathically subdue his step-brother, and Juggernaut was returned to his stasis tank.

Months after that, Mystique apparently again sabatoged the stasis tank, requiring Xavier to leave his mansion and repair the tank. This gave her, win her guise of Risty Wilde, enough time to trick the X-Men into having a wild party and a young man calling himself Arcade into getting him information on the New Mutants, as well as possibly other secrets of the X-Men. For the good of Xavier, the X-Men, and quite possibly all humanity, the stasis tank must remain working, but mechanical systems do have their ways of failing...