Vali (pronounced like the English word “valley”; from Old Norse Váli) is a Norse god whom we know only from a few scattered, passing references in Old Norse literature. He’s the son of the god Odin and the giantess Rindr. When the god Baldur was killed, Vali avenged his death by killing Baldur’s slayer, another obscure divine figure named Hodr (Höðr).
Vali performed this feat when he was only one day old, and Vali may have been born specifically for this purpose, although the sources are ambiguous on this point. The only other mention of Vali apart from his role in avenging Baldur’s death comes from a poem that lists him among the younger generation of gods who survive Ragnarok, the downfall of the cosmos. (In some accounts of Ragnarok, that is; in other accounts, the universe just ends, and no one survives.) This lack of other episodes from Vali’s life could lend support to the idea that he was born only to kill Hodr, but it could also simply be due to the fragmentary nature of the sources themselves.
The meaning and etymological origins of Vali’s name are unknown. The most convincing theory that has so far been put forth is that the name is derived from the Proto-Germanic word *waihalaR, “The Arguing One,” which connotes disputation and ultimately combat.
He may or may not have been actively worshiped by the Norse and/or other Germanic peoples (as opposed to being a merely literary figure). There is a location in Norway named Valaskioll, which comes from Old Norse Valaskjálf, “Vali’s Crag/Seat.” This might suggest that the area was a place where Vali was worshiped. But the name Valaskjálf is elsewhere used in a more general sense to denote a dwelling-place of the divine, so this place name could also refer to a more general religious center, or could have been used simply to express a desire on the part of those who named it to live in close proximity to the gods. The significance of this name, like most of Vali’s personality, deeds, and role in Norse mythology, will forever remain a mystery to us.
Looking for more great information on Norse mythology and religion? While this site provides the ultimate online introduction to the topic, my book The Viking Spirit provides the ultimate introduction to Norse mythology and religion period. I’ve also written a popular list of The 10 Best Norse Mythology Books, which you’ll probably find helpful in your pursuit.
 The Poetic Edda. Baldrs Draumar, stanza 11.
 The Poetic Edda. Hyndluljóð, stanza 29.
 The Poetic Edda. Völuspá, stanza 23.
 Turville-Petre, E.O.G. 1964. Myth and Religion of the North: The Religion of Ancient Scandinavia. p. 139-140.
 The Poetic Edda. Vafþrúðnismál, stanza 51.
 Simek, Rudolf. 1993. Dictionary of Northern Mythology. Translated by Angela Hall. p. 348.