Diabolist
A diabolist is a character who has aligned himself with the Infernal Realm in return to dark powers. Formally, diabolist is a Mythic Companion, described in Realms of Power: The Infernal p. 112. The title is often used to describe any character with Infernal allegiance, however.
References
- See "Mythic Companion: The Diabolist", Realms of Power: The Infernal page 112.