Dev was away from home with his brothers Gilbert and Bastien and his sister Aimee when Arcadians hunted down and killed Gilbert so that he couldn't complete the mating ritual with their sister. Bastien was also killed and Dev was forced to flee to protect young Aimee. Dev and Aimee never got over their survivors' guilt. Furthermore, Mama Lo told him that she wished he had been the one killed instead.
When the Peltiers opened Sanctuary, Dev became the bouncer. That's how he met Samia. He is the only person she can't read through telepathy or psychometry, so his presence brings her peace. They mated and bonded, but Samia chose not to take back her soul because she wants to remain immortal. Savitar's bonding gift was the ability to conceive, which is normally not possible for Dark-Hunters. They don't have any children yet.
Dev is a pretty good sidekick on quests. He helped Aimee locate and kill the Daimons that had stolen pieces of Fang's soul. He also helped Samia retrieve Hippolyte's girdle from another realm. Dev is a ferocious fighter when necessary, but he can also break the tension with a well-timed wisecrack.