Marcus was the son of Immortus. Sired and raised in the inter-dimensional realm Limbo, Marcus grew bored with his limited existence and used his father's machines to seek a means of escape. While observing Earth from afar, Marcus saw the Avengers and became enamored with their newest member, Ms. Marvel. Using his father's devices, Marcus snatched Carol from the timestream and brought her to Limbo. There he tried unsuccessfully to woo her and finally used mind-manipulating devices to force her to love him. He then "impregnated" Ms. Marvel with his own essence so that he might be reborn on Earth. Marcus blocked out Carol's memories of her time in Limbo and left suggestions in her mind that would make her love him when he emerged on Earth. He then returned Carol to the exact point in time from which he had abducted her.
Less than a day later, while explaining her views on child-bearing and superheroics to the Scarlet Witch, Ms. Marvel collapsed. When Wanda rushed her to the hospital, Carol learned that she was nearly four months pregnant. Carol knew that there was no way she could possibly be pregnant. She was shaken and devestated by the news, as both a hero and a woman. Despite their surprise, the Avengers were wildly enthusiastic about Carol's pregnancy. Carol herself was angry, bewildered and scared. Within the day, Carol's pregnancy had run its course. The child she gave birth to continued to grow and develop at an extraordinary rate. He named himself "Marcus" and asked the Avengers to provide him with various devices and mechanical components. Marcus quickly realized that he had miscalculated his impact on Earth's temporal state. Because of his arrival in our timeline, New York became plagued by a series of temporal anomalies, from armored knights to prehistoric dinosaurs. As the Avengers battled the time-displaced creatures, Marcus toiled on the device that would enable him to remain on Earth. When Carol met her "son," she was struck by an uncharacteristic wave of emotion and instantly "fell in love." When the Avengers inadvertently destroyed Marcus' device, he was forced to return to Limbo. Carol, completely in Marcus' control, agreed to accompany him, much to the Avengers' surprise. Once in Limbo, Marcus continued to age at an unnatural rate. Before he knew it, he was too senile to correct the problem and save himself. Once Marcus had died, Carol was free from his control and overwhelmed with disgust and anger over his abduction, rape and manipulation of her. Mastering Immortus' devices, Carol returned to Earth and planned to start a new life in San Francisco, unable to face the teammates who had failed her.