Nearly a quarter-century ago, two extraterrestrials came to Earth for unrevealed reasons; it is unclear if they arrived together or separately, but a few years later the pair, called Frank and Leslie Dean, were a married couple with acting careers. Five years later, the Deans and five other Californian couples---criminals Geoffrey and Catherine Wilder, time-travelers Dale and Stacey Yorkes, mutants Gene and Alice Hayes, scientists Victor and Janet Stein, and sorcerers Robert and Tina Minoru - were teleported before the gigantic Gibborim, who planned to eradicate humanity. They charged the twelve to provide sacrifices of human souls for the next twenty-five years, after which six of them would receive immortality. Calling themselves the Pride, the twelve established covert dominion over Los Angeles and other regions. Three years later, the Pride decided to have children to whom they would cede their immortality, and about a year later Karolina was born. A few years after this, the Fantastic Four's debut heralded a wave of overt superhuman activity, but the Pride, for the most part, avoided confrontations with Californian super heroes.

The Deans worked to give Karolina a normal childhood untouched by Hollywood scandal; when she was four, they gave her a bracelet which secretly suppressed her alien abilities. Neither Karolina nor the Pride's other children - Chase Stein, Alex Wilder, Gertrude Yorkes, Nico Minoru, and Molly Hayes - suspected their parents' activities. In recent years, the Deans conspired with the mutant Hayeses to betray the Pride, hoping only they and their daughters would receive immortality. A year and a half later, when Karolina was sixteen, she and her friends discovered their parents' latest murder; Alex Wilder, having learned of both the Pride and the planned coup a year before, manipulated his friends into searching their homes to acquire weapons. During their investigation, Karolina discovered her alien heritage, and most of her friends also developed powers or discovered advanced technology. The six runaways resolved to become heroes, most of them using codenames; however, when they attempted to stop the Pride from offering the Gibborim their latest soul, Alex betrayed them to protect his parents from the Dean/Hayes coup. The Gibborim slew Alex and destroyed the ritual site; the other Runaways escaped.

For months Karolina struggled with her identity, being both an alien and a lesbian. She fell in love with her best friend, Nico Minoru, only to suffer a rejection. This was timed with the arrival of Xavin, a young Skrull prince who had been betrothed to Karolina by her parents without her knowledge. Karolina discovered that her parents had been exiled from their homeworld, Majesdane, for inciting a war with the Skrulls. Xavin wanted Karolina to join him in hopes that their marriage could bring peace, but she initially declined his proposal because of her sexual orientation. She agreed after Xavin used his shape-changing abilities to become a woman. Curious about her homeworld and hoping to end the ongoing war, Karolina reluctantly left the Runaways for space.

Karolina fell in love with Xavin, and for a time the two were able to arrange a cease-fire between their races. Though the wedding plans went smoothly, an attack during the actual ceremony forced the couple to flee to Earth, and Karolina and Xavin have re-joined the Runaways.