A Bourreau (処刑人, Burō) is term from Jun Mochizuki's The Case Study of Vanitas. It refers to a Vampire who is tasked with being an executioner of their own kind, employed by the Vampire Senate to dispose of certain Vampires who are perceived as a threat or hindrance of some sort to Vampiric society. Bourreaus are formed of Vampires whose ancestors have committed some great and terrible crime, which they themselves must work to atone for by devoting their lives to hunting down their fellow man. The nature of a Bourreau's duty means they are the object of resentment and fear among Vampires, making each one very isolated individuals.
SPOILER WARNING!
This article contains plot and/or ending details for The Case Study of Vanitas. Read at your own risk.