The Monk is a vampire along with his assistant/ sister Dala. The Monk was once a post-Civil War plantation owner in New Orleans named Louis DuBois. He and Dala are attacked by their vengeful ex-slaves and subjected to a voodoo ritual which transforms them into the undead. They move to Gotham where they lure Batman into a trap by using Bruce Wayne's fiancee, Julie Madison, as bait. The Monk places Julie in a hypnotic trance. After rescuing Julie, Batman kills the Monk and Dala by shooting them with silver bullets as they lay in their coffins.
Dala later appears alive and romantically engaged with Dick Grayson as part of the Monk's plan. Batman is transformed into a vampire by the Monk but is eventually cured by a serum administered by a priest/exorcist named Father Green. In the end, Father Green leaves Gotham with the Monk and Dala as his captives, suggesting that he had been pursuing them for a large time period.
Batman and the Mad Monk
This version of the Monk is called Niccolai