It seems there may be two gods named Vali throughout Norse mythology. Most sources refer to them as Vali I and Vali II. There are enough similarities between the two to make the argument that they may be the same deity, but since the lineage is very different, as are other circumstances, the opposite argument is also entirely plausible. For these purposes, I have addressed them separately here.
Vali I is the youngest son of Odin with the giantess Rinda (also called Grid). He is a member of the Aesir, and the God of Vengeance. Some believe he was born with a specific purpose: to avenge Balder, which he did when he was a day old by killing Hodr (who slayed Balder) with his arrows. Balder had been having terrible nightmares, so Odin made a trip down to the Underworld to seek knowledge about them from a sybil. The sybil confirmed to Odin that Balder was destined to die, but that he would be avenged by another son of Odin, one who had yet to be born. That son was Vali, and his mother would be Rinda. Odin had sent a Hermod, a messenger of the gods, to learn even more from a wizard in Lapland. The wizard, Rostioff, did not welcome the messenger, and tried to slay him, but Hermod was able to outsmart him and bound him with his own rope.
Vali II was the unlucky son of Loki and Sigyn, and there is not as much written about him, and it’s possible he’s another variation of Vali I as the stories have similarities. Some sources describe Vali II’s origins as the same as Vali I. He was used to avenge Balder, but some versions of the story go on to tell of the Aesir turning him into a werewolf so they can capture Loki. After he is turned into a werewolf, he attacks and tears out the throat of his brother, Narvi. Vali then used Narvi’s entrails to trap Loki and bind him to rocks. Some accounts reverse this, where Narvi is the wolf, and Vali is the one whose entrails bind Loki.
Different researchers are not sure that revenge was the entire purpose of his existence, but it’s generally agreed that this was his main purpose. Vali is also one of the younger generation of gods who survive Ragnarok, and the minor listing that he’s given in a poem about that supports the idea that he may have existed only to kill Hodr, but the sources are fragmented, so it might not be. What we do know is that Vali is in charge of retribution and revenge.
The Norse saw Vali I in particular as a representation of the light, and worshiped as an archer because his arrows represented beams of light. He is known as the light bringer, and an old Norwegian calendar designates a month for him called Lios-beri, which would have fallen between mid-January and mid-February in reference to the modern calendar.
There is some evidence that Vali was worshiped among the Norse and other Germanic peoples. There is a location in Norway called Valaskioll, which comes from Old Norse “Valaskjálf,” which translates to Vali’s Crag or Vali’s Seat, so some believe this is a place where he may have been worshiped. However, Valaskjalf may not refer to one particular deity, but simply to a place where divinity may dwell. It may just be a place that’s close to all the gods, not just Vali.
Whether or not they are the same deity with different accounts, or two different ones with the same name, Vali is a deity who may seem like a side player in the stories, but he is important to some of the bigger moments in Old Norse stories. After all, not every deity would be able trap Loki and slay Balder! I would want him on my side in a battle.