Vengeance demon

Vengeance demons are a group of beings that appear in the TV series Buffy the Vampire Slayer. They are immortal women who travel the world exacting grisly vengeance on behalf of victims, such as scorned women or neglected children. Their typical method is to appear to a wronged person in the form of a human female, and encourage them to vent their spleen about those who have hurt them. The moment the object of the demon's attention expresses their preferred method of punishment in the form of a wish, the vengeance demon can cause his or her wish to come true, whether it requires gruesome dismemberment or even the creation of a new alternate universe.

Two vengeance demons have appeared in Buffy the Vampire Slayer: Anyanka (also known as Anya) and Halfrek (sometimes known as Cecily