Caitlyn was an accident in every possible sense of the word. Her mother Koschei never realised that she had regained the capacity to conceive after it was taken from her by the mystic augmented tortures inflicted by the Hand of Glory. Her unrealised presence during the mission to take down Eva Kraus and the Hand saw the Ice Queen entity trapped within the prison of Koschei's  womb, replacing the soul the child would have had with itself but being rendered dormant in the process.

The pregnancy was a troubled one, the unborn child forced to endure the depredations of  the Architects of the Fringe and the ravages of the psion plague, which saw Koschei first comatose for months then actually dead until her Fringe-enhanced mystic immortality knocked the process askew: like her mother, Caitlyn's blood acts as a counter agent to the psion plague, which while not a cure per se, stops any psion innoculated with it from being contagious. Despite this Caitlyn is born an apparantly perfectly normal and healthy baby girl.

For a while, things were good. Koschei and Valentina were doting parents, the andogyne Cathayan an enthusiastic benefactor. But that changed when Koschei uncovered the hidden location of the Monolith, a secret she kept from the Conspiracy but shared with Cathayan in order to provide the Areophany Project with a secure base. The day after her first birthday, Caitlyn started to age rapidly as the power of the thing that had been Eva finally began to stir. Suspecting the Ice Queen might be responsible, Koschei doesn't mention it to anyone except Valentina as she seeks help from friends within the Guardians of the Whispering Knife. The search of their archives however allows members of that organisation to deduce the truth - just as EDEN burns the cloak.

As the Conspiracy falls apart from within and without, there remains those in a position to organise a response: kill the child. Cathayan provides the means for mother and child to escape that final confrontation while Valentina & Koschei's allies within the Guardians b the time. But it was the Assassins that provide the solution. They bind the entity fast until the end of days, remove its memories of itself, and train Caitlyn in their arts while helping Koschei slay those who hunt her and her daughter. In return, when the time came, the two of them have to kill a certain man whose identity is remains unknown.

Scant years after her birth, Caitlyn is now almost an adult. While her stolen childhood weighs heavily on Koschei, it barely seems to impinge on her at all - there's no anger, no regret. Fanatically loyal to her mother, unhesitant to take any life she's order to do so, she lives her life for the moment in a body shaped by the taint of the supernatural augmentations of both her mothers one of whom she's never even met. She's a good girl - but every so often, when her mother's not looking, the thing inside her tests its bonds.

Of all the Ultimates, she's only met Rowena, carelessly saving the life of someone who might as well be blood sister to her. Knowing that Rowena was in the process of restoring her other mother to her wouldn't have made the slightest difference: Caitlyn saved Rowena because it was fun. And she's met the Boy, a mystically enhanced killer just like her, working for people who may at any moment prove to be the Enemy. But he's something else even more dangerous. He's someone she's in love with.