Norse Mythology: He was a son of Odin and Grid (a giantess), and had a twin brother named Vali. He dwelled in Vidi. He was one of the strongest of the gods and can be considered a god of vengance. In the ragnarok he will avenge his father by killing Fenris. He is one of the Aesir who will survive the final battle.
(Nicole Cherry, A list of Norse Beings, http://www.ugcs.caltech.edu/~cherryne)