A character in the X-Men universe, more notably, one of the most phyically strong characters (as the glorious althorrat as pointed out, Juggs isn't a mutant, per se) on Earth.

Cain Marko is Charles Xavier's stepbrother. He grew with envy for Charles, until, when at Korea in the War, entered a cave and read some words that were laying on a stone. Holding a red gem, he received the mystical powers of the wizard Cyttorack. Since then, Cain is one of the X-Men most fearsome enemies, and only mental attacks can stop him. He allied with Black Tom Cassidy, and both became best friends. Once, Juggernaut jumped into the raging sea just to save his pal. He fought the X-Men and other Marvel heroes (such as Spider Man) in the coming years.

When Onslaught came, Cain was his first victim, since that being was composed by Xavier's repressed hates. He put Marko inside his gem, where he had to fight demons and the ruler of Cyttorack. With the help of Gomur, the ancient, the Juggernaut managed to escape, and the gem forever imprisoned inside him. To relax, the behemoth took a small town and attacked by D'spayre and his sister. He was reduced to a being of pure hate in that fight, showing that really no force on Earth-except mental-could stop him. The next time he showed up, he told the X-Men that, without Xavier to take care of his properties, he would be the owner and administrator of all the Xavier Institute. The team expelled him from the mansion this time, but he appeared once again, with his friend Black Tom Cassidy, trying to retrieve his Gem of Cyttorack from a group of monks. Since then, the duo is missing and at large.