Cain Marko is the son of Kurt Marko, who becomes Charles Xavier's stepfather when he marries Sharon Xavier after the death of her husband Brian, for which Kurt is partially responsible. Kurt Marko favors Charles and abuses his own son, Cain. Cain resents Charles and bullies him frequently. Cain Marko and his step-brother Charles serve in the US Army and are stationed in Korea. Marko finds a hidden temple dedicated to the entity Cyttorak. On entering, Marko finds and holds a huge ruby and reads the inscription on the stone aloud: "Whosoever touches this gem shall be granted the power of the Crimson Gem of Cyttorak! Henceforth, you who read these words, shall become ... forevermore ... a human juggernaut!" The gem channels Cyttorak's power into Marko. The transformation causes a cave-in, and the character is buried and presumably killed, not being heard from again until a sudden assault on the X-Men's headquarters.