Executioners
When a Divine Assassin is no longer needed or fails to behave as expected, His Shadow calls on a special subset of Divine Assassins called Divine Executioners. Divine Executioners are far more deadly than regular Divine Assassins. As Kai said, "If Divine Assassins are Death incarnate, then Divine Executioners are the Apocalypse made flesh." These two classes compete for protoblood. An interesting paradox develops here because Divine Assassins are designed to be immortal, to always survive, a concept developed in episode 18 of season 4, "The Game."
Read more about this topic: Divine Assassin