Cai (Caitirin Aria Kerian) is 147 years old. She is an immortal. She was born in 1858 to two immortal parents, Tristan Alec Kerian, an old Roman born about 50 years before Christ, and Eugenie Monteval, a French woman of a certain age.

Cai, unlike many girls her age and in that time, was not sent away to school and instead was tutored at home by her mother and father. Her mother tried valiantly to teach her music, but Cai has been hopeless at music since birth. She enjoys listening to it, but cannot play an instrument nor sing very well. She can sing along to the radio and not make babies cry, but her singing stops there. Her father taught her Greek and Latin, and she also speaks French, Italian, and Russian. He also taught her history, philosophy, mathematics, science, and other subjects he thought would serve her well.

When she was thirteen years old her mother was viciously murdered by her uncle who had been taken by fits of madness. Her father killed him and has raised Cai by himself ever since.

Cai handled her mother's death with surprising maturity and was almost the sole reason that her father survived the episode. Without a young daughter to care for he probably would have vanished. He has been devoted to Cai ever since, and has never taken another wife or companion of any kind.

When Cai was thirty years old she left home and began to train as an assassin for the Council of Elders, a group of immortals whose history extends further back than human recorded history. She excelled in this field and rose quickly through their ranks, becoming one of the most skilled assassins before she was fifty years old. Her father did not approve of her chosen vocation and they often argued about it in her early years. Tristan eventually gave up trying to argue the point for fear that she might vanish and he would never see her again.

Over the years, Tristan began to acquire businesses and make shrewd investments. He was eventually to become one of the most powerful, but least known, men across the globe. As generations passed he would seem to die and pass on the running of the business to a younger family member, thereby disguising his immortality and ensuring that all of his businesses were run up to his standards. He was a great philanthropist and humanitarian, but always remained anonymous. Most people would never know that he was their benefactor. Many of the enterprises underneath his auspices are not publicly known to be.

During WWII Cai was on assignment in the Pacific Theater, travelling and making things happen behind the scenes as the Council of Elders pulled strings to manipulate the politics of the mortal world as it tore itself apart in the wars. While Cai was on a mission she fell hard for a soldier who was serving where she was. She felt like she'd met the one person she could spend the rest of her life with: the person who would be to her like her mother had been to her father.

He was killed in an air raid when there wasn't enough shelter around. Cai had been visiting him only minutes before and had kept him later than he was supposed to be. Ultimately she felt partially responsible for his death and was devestated. She had maintained contact with her father over the years, but shortly after her soldier was killed, she vanished completely for about twenty years. No one to this day, except for Cai, knows where she was from 1944-1967. In 1967 she resurfaced in tears, covered in blood, at one of Tristan's many homes and spent about a year recovering from something she never spoke about even to her father.

She went back to working for the Council of Elders, but she wasn't the same person she had been before the war. She was bitter and angry and prone to dangerously dark moods and much more violent. The Council sent her on some of it's worst and most dangerous missions. Only the omnipresent threat of Tristan Kerian and the power that he weilded kept them from having her killed.

But after some time, even that threat proved not great enough to keep them from putting out the order.

They tracked her down and nearly burned her to death. They would have killed her if her one and only friend, Simon Frost, hadn't been supposed to meet her for drinks and called her father. With the help of Mandala, an organization dedicated to the rescue of unfortunates, immortal ones, she would be dead. It took months for her to recover. It was at Mandala that she met Mei Shibata, who has had the dubious honor of becoming Cai's second real friend. And possibly something a little bit more. Something Cai had become convinced that she'd never find again.

And the rest they say, is yet to be written.