Cain Marko is the son of Dr. Kurt Marko, an atomic researcher. Cain's parents separated and Cain was eventually sent to a boarding school.
Kurt Marko's colleague, Dr. Brian Xavier, another atomic researcher, died in an accident, and Kurt Marko eventually married Xavier's widow
Sharon for her great wealth. On marrying Sharon, Kurt Marko moved into her large Westchester County mansion, where he lived with her and her
young son Charles. Cain, who had become a cruel and spiteful boy, came to live at the mansion as well.
Cain immediately began bullying his new stepbrother Charles. But Cain was often secretly beaten by his abusive father. Charles' vast telepathic
powers were beginning to develop, and on one occasion he found himself experiencing the anguished thoughts and emotions of Cain after Cain had
been beaten by his father. The inexperienced young Charles could not control or end his contact with Cain's mind at this time. Somehow Cain
sensed that Charles was reading his mind and had discovered his secret shame. Cain believed that Charles had invaded his thoughts deliberately,
and from then on Cain regarded Charles as his enemy. Cain was abusive to his stepbrother at every opportunity.
Getting into a disagreement with his father over money, Cain accidentally upset some explosive chemicals and caused a fire to engulf his
father's home laboratory. Though Kurt Marko managed to rescue both Cain and Charles from the fire, he himself died of smoke inhalation.
Sharon Xavier Marko had died sometime before, tormented by the lovelessness of her marriage to Marko. Cain Marko continued to live in the
Xavier mansion, growing increasingly resentful of his stepbrother's scholastic and athletic achievements as wall as of his telepathic powers,
which Xavier mastered as he grew older.
What happened to Marko after he left home is unclear. However, it is known that he became a mercenary and was eventually imprisoned in a
Third World jail when the revolutionary forces he was fighting for were defeated. In the jail he became friends with a fellow mercenary, Black
Tom Cassidy, who used his mutant powers to help them escape.
Later, Marko and Xavier found themselves serving together in the same U.S. military unit in Asia. Marko deserted under fire and Xavier went
after him to bring him back. Xavier followed Marko into a cave that housed the lost secret temple of Cyttorak, a powerful mystical entity.
Marko impulsively grabbed a glowing ruby from the lap of an idol and read the inscription (which mystically appeared to his mind to be in English):
"Whosoever touches this gem shall possess the power of the Crimson Bands of Cyttorak. Henceforth, you who read these words shall become forevermore
a human juggernaut." As Xavier watched, the gem's mystical power transformed Marko into a larger, superhuman being. Just then enemy high explosive
bombardment caused a cave-in, and Marko was buried under several thousand tons of rock. Xavier survived and returned to his unit.
Marko, now the Juggernaut, eventually dug himself free with his newfound power and made his way to America to use his power to kill Xavier.
He was defeated by Xavier and his original team of X-Men. Over the years the Juggernaut has clashed with Xavier and both the original and new
teams of X-Men repeatedly. He has also formed a successful criminal partnership with his old friend Black Tom Cassidy.
More recently the sentient psionic being known as Onslaught, actually an amalgamation of the psyches of Xavier and Magneto, would-be world
conqueror and mutant Master of Magnetism, ripped the Crimson Gem of Cyttorak from Juggernaut's body and imprisoned him within. Inside the
jewel, Cain learned he was an avatar for Cyttorak. As such, the otherworldly entity sought to assume control of Juggernaut's form. But Cain,
through sheer force of will, destroyed the evil god and returned to Earth, stronger than ever, but unable to fully control his amplified abilities.
Cyttorak was merely one of a pantheon of eight gods, all with earthbound avatars. These Exemplars enlisted the Juggernaut's aid in constructing
a machine that would enslave the human race. As the Exemplars tended to in their final preparations, Cain withdrew deep into himself, where he
clashed with Cytorrak. Charles entered his stepbrother's mind to aid him in the battle, but the Exemplar known as Bedlam sensed his presence a
nd expelled him. Still, Charles' short stay in Juggernaut's head had helped Cain regain control of his psyche. After defeating Cyttorak, Juggernaut
destroyed the Exemplars' God Machine. He then turned his attention to the avatars themselves, defeating each in turn.
Juggernaut again was cast as a hero when the sentient spaceship Prosh escaped the confines of a Celestial prison, returned to Earth and dispatched
a group of disparate beings on a journey through time to uncover the keys to preserving human evolution. Besides Cain, Prosh's task force included
Phoenix and Iceman, members of the X-Men; and Mystique and Toad, mutant terrorists. Their mission: Save the human race from a threat that might
not manifest itself for millions of years. Juggernaut was shown that for all his physical strength, he long has lacked strength of character.
Despite all his yearning for power, he has squandered his supernaturally enhanced abilities. When Prosh reassembled the members of his team in
the present, they fought and defeated the enigmatic alien entity known as the Stranger, who sought to control the natural evolution of humans
and mutants. If not acquiring a newfound respect for life and human dignity, at least Juggernaut gained a better sense of understanding for the