Váli is the name of two entities in Norse mythology.
Son of Odin
Váli is a god in Norse mythology. He is the son of Odin and Rindr, a giantess or human princess. He was born specifically to kill his half-brother Höðr and avenge another half-brother, Baldr. He grew to adulthood in one day and will survive Ragnarök.
Son of Loki
Váli is also a son of Loki and his wife Sigyn. His brother is Narfi. After the Æsir found that Loki had engineered the death of Baldr, one of their own, they expelled him from Asgard. He fled from them for a while until they caught him and decided to punish him. They changed Váli into a wolf, which then killed Narfi. The gods used the tendons and entrails of Narfi to bind Loki to a rock and hang a serpent above his head until he would break free at Ragnarök.