Gullveig is an evil goddess, one of the Vanir. She causes misfortune and death wherever she goes. Gullveig may be immortal, since the gods have tried to kill her several times with fire and spears, but she still lives. Loki ate a piece of her heart, and it causes him to do evil things. Her name means "Gold Might".
Gullveig is associated with Freya, appearing either as her attendant, or as an aspect of the goddess.