1911 Encyclopædia Britannica/Alastor
ALASTOR, in Greek mythology, the spirit of revenge, which prompts the members of a family to commit fresh crimes to obtain satisfaction. These crimes necessitate further acts of vengeance, and the curse is thus transmitted from generation to generation. The word is also used for a man’s evil genius, which drives him to sin without any provocation; a man so driven is sometimes called Alastor. The epithet is applied to Zeus and the Erinyes as the deities of revenge and punishment.