Demetri is a member of the Volturi Guard, a vampire, an honorary member of the Seely Court, and the husband of Lyra.
Crimson Twilight[]
In Crimson Twilight, Demetri first meets Lyra, and begins to have an interest in her. During the process of courting her, he gets pulled into a whirl-wind of events, causing him to get married, change his wife into a vampire, and help run the Seely Court.