Since losing his lover and unborn child to Gilles de Rais’s experiments, and since becoming a vampire himself, Tristan has become twisted. He has spent centuries hating his lord and maker, failing to kill him, and becoming obsessed with retrieving the child he lost. Although he appears to be in control of himself, he acts in extreme ways and hovers on the side of evil out of loneliness and paranoia.
As one of the oldest vampires alive, he was contacted by Mayor Yu Wong to exert his influence and sponsor her project. Ever the manipulator, he broke Eve and Cain apart to achieve his goals. He opens up to Eve gradually, but goes catatonic when he has to face Gilles de Rais again. In the end, Eloise seems to be the only one able to save his soul.