Grendel's Mother

Grendel's Mother (also sometimes called "Hag" in the old Viking Beowulfsaga) is one of the main villains in the Viking saga Beowulf as well as its many retellings over the years: she has varied between a hideous old hag to a seductive femme fatale (similiar to a siren) but has always remained consistant in her motives - to avenge the death of her son Grendel at the hands of the Viking hero Beowulf.

Grendel's Mother has always been associated with the water and may well of been based on an ancient Slavic water-goddess or spirit: at any rate the monster attacked Beowulf and attempted to drag him to a watery grave (at least in the originally telling of the story) but was defeated by Beowulf in an epic struggle.

However in the modern retelling of Beowulf made famous by the CGI film, Grendel's Mother was not killed by Beowulf and went on to torment him for a great portion of his life: this is inconsistant with the old Norse saga - in which Beowulf slew her only to die years later at the hands of a dragon.