Norse Mythology: Daughter of Loki and the giant Angurboda. She is the sister of Fenrir (Fenris-wolf) and Jormungand (Midgard serpent). She is the goddess of the underworld. Her realm was Niflheim and her hall, Elvidnir [misery]. She was described as half white and half black.
(Nicole Cherry, A list of Norse Beings, http://www.ugcs.caltech.edu/~cherryne)