Callestina, known in modern times as Cynthia VanDervane, was born in AD 387. She was the adopted sister of Alaric I, king of the Visigoths.
As a young woman, Callestina fell in love with Darius. When she was 22, Darius brought his army to winter with Alaric's while they prepared to invade Rome, and she became his semi-secret lover, as it seemed only Alaric and his people were unaware. She spent her nights with him until the following year, when the two armies departed to attack Rome. Determined to prove herself worthy, Callestina followed the armies. When she was discovered, it was too late to send her back. She was unaware that Darius was not only indifferent to her presence, but had come to consider her clingy and annoying
Grayson, who had fallen in love with Callestina, swore to protect her. However, when the battle to take Rome was going strong, she convinced him to join the fray at Darius's side. Unable to bear not knowing any longer, she rode into the city, only to meet her first death by an arrow. Grayson saw her fall, and brought her to safety on Holy Ground. After she recovered, he took her back to the camp outside of the city. Though he had warned her that Darius loved no one but himself, she never believed him.
When the battle was over, Callestina went to Darius, believing they could live together forever in peace, at which point he made it clear that he had never loved her. She intended to cry her heartbreak and pain to Alaric, but Grayson stopped her. He told her to live, then left with Darius.
Darius, Grayson and the army headed for Paris, intending to make that the seat of his Immortal Empire. There he fought Emrys, the oldest immortal at the time, and beheaded him. The power of Emrys' Quickening, however, changed Darius completely, and he became a peacemaker - the only known example of a Light Quickening.
Grayson could not understand the change, he even offered his head in hopes that it might restore Darius, but finally realizing that would not happen, he turned on his teacher. He left Darius and nearly rode his horse to death going back to Callestina. He told her what had happened, and asked her to join him so that they could destroy Darius, and create the Immortal kingdom of which Grayson dreamed. To pacify Alaric, he married her before they left together.
Callestina spent years alternately with Grayson, and living in Paris trying to destroy Darius's reputation and his works. She was never successful. She remained Grayson's lover, his confidant, his student. Between the two of them, they kept their hatred and the bitter pain of the perceived betrayal by Darius alive.
After Duncan MacLeod took Grayson's head, and Darius' head was taken by Hunters, the feelings of hatred and pain were not ended, and Callestina, now calling herself Cynthia VanDervane, sought out and became the lover of Victor Paulus because he was Darius' last student. She intended to destroy all of his efforts to help people in the world, frame him as a betrayer of his own cause, and murder him after making certain he knew she was responsible. Her plans were stymied by Duncan MacLeod, and in order to carry them out she would have to have exposed herself.
MacLeod learned from Joe Dawson that Cynthia had consistently tried to destroy Darius' work over the centuries, and he realized she was linked to Grayson. Joe confirmed that. Duncan warned her off of Victor but he let her go to say goodbye to Victor. This error cost Victor Paulus his life, and Cynthia invited Duncan to face her in the place Grayson had died. He defeated her and took her head.