Baldrs draumar has Odin ride to the underworld to interrogate a dead seeress, and the answers he extracts include a piece of information about a person who does not yet exist. Rindr will bear Váli in the western halls; that son of Odin will kill when one night old; he will not wash his hands nor comb his head until he has borne Baldr's slayer to the pyre.
Conceived, born, grown and finished with his life's work inside twenty-four hours.
Vengeance as procedure
The one-night child is not a display of divine power. It is a compressed version of a legal and social obligation that Norse literature takes extremely seriously, and every detail of the stanza is technical.
The refusal to wash or comb is a recognised state. Grooming was a marker of ordinary social participation, and abstaining from it signalled that a man was under an unfulfilled obligation of vengeance — the same gesture appears in the heroic poems, and in Völuspá's account it is Odin's son who does it. A avenger in that condition is visibly outside normal life until the debt is discharged.
What the miracle does is remove the delay. Norse vengeance is normally slow: a killing creates an obligation that may take years to fall due, waiting for a son to grow. Váli is that structure with the waiting deleted. He is not a character. He is the mechanism itself, given a name and a single night to operate in.
That is also why he has no personality, no dwelling described in Grímnismál under his own name, no attributes and no other story. He kills Höðr and then simply exists among the survivors.
Rindr, and how Odin got her
His mother is Rindr, and the corpus preserves two very different accounts of her.
The Icelandic sources say almost nothing: a name, and a location in the western halls. The skald Kormákr Ögmundarson, in the tenth century, has an obscure half-line referring to Odin winning Rindr by spells, which suggests a known story.
Saxo Grammaticus tells that story at length in Gesta Danorum Book Three, and it is one of the most unpleasant episodes in his work. Othinus, needing a son to avenge Balderus, learns from seers that Rinda, daughter of the king of the Ruthenians, must bear him. He goes to her court disguised as a soldier and wins a battle; she refuses him. He returns as a smith and offers her jewellery; she slaps him. He returns as a young warrior; she rejects him again. Finally he comes as a woman, a healer named Wecha, gains a place among her attendants, and when Rinda falls ill has her bound to her bed on the pretext that the medicine will cause violent reactions. Then he rapes her.
Saxo does not approve. He has the other gods expel Othinus from his position for the outrage and for the indignity of the disguise, and he is restored only after an interval. It is one of the very few places in medieval literature where a Norse god is judged by his own pantheon.
Whether this is a Danish tradition the Icelanders knew and suppressed, or Saxo's own elaboration of a bare hint, is not resolvable. The bare hint is genuine — Kormákr's verse is two centuries older than Saxo — but nothing establishes that it referred to this.
Two Vális, and a permanent confusion
There is a second Váli, and he is Loki's son.
At the end of Lokasenna and in Gylfaginning, the gods capture Loki and take his two sons by Sigyn. Snorri's version: the Æsir transformed Váli into a wolf, and he tore his brother Narfi apart, and Narfi's entrails were used to bind their father to the rocks.
So the name is used twice, in the same body of texts, for a son of Odin who kills to avenge a brother and for a son of Loki who is made to kill his own brother. Both killings are one-off acts of family destruction, and both are the mechanism by which a story reaches its punishment.
Some manuscripts and editors reverse the brothers' roles or use the form Áli for one of them, and the Eddic reference to the fetter's material names no one at all. The confusion is in the sources themselves and cannot be edited out, and the family tree marks both figures separately for exactly that reason.
Saxo's Bous
In Gesta Danorum the avenging son is not called Váli at all but Bous, and he is a considerably more substantial figure: he fights Høtherus in a full battle, mortally wounds him, and dies himself the following day of his own injuries, mourned by an army that buries him in a great mound.
Compare that with the Icelandic version — a one-night-old child who kills and then is never mentioned again except in a list of survivors — and the difference is the whole difference between the two traditions. Saxo is writing dynastic history and needs a warrior; the Eddic poets need a piece of cosmic bookkeeping.
What survives of him
Váli lives through Ragnarök alongside Víðarr, and Vafþrúðnismál places them together in the sanctuaries of the gods after Surtr's fire goes out. There is no cult evidence, no place-name, no amulet, and essentially no modern reception outside occasional video-game appearances.
He remains one of the clearest illustrations of something worth understanding about this mythology: some of its figures are not characters at all, but the shape of an obligation given a name because the story required one. For the death that summons him, see Baldr; for the wider tradition, the Norse overview.
Why does Höðr have to die when the killing was not his fault?
Because Norse vengeance follows the deed rather than the intent. The obligation attaches to the hand that did it, and Völuspá and Gylfaginning are both entirely uninterested in Höðr's blindness as a defence. Compensation could substitute for blood in ordinary Icelandic law, but no settlement is offered here, and the gods are on hallowed ground where they cannot act immediately in any case. The result is a system that produces a correct outcome and an unjust one simultaneously, and the poems record it without protest.
Is Váli's name related to anything?
It is usually connected to a root meaning slaughter or the slain, the same element as in valr and valkyrja, which would make him something like "the one of the slain" — a name that is a job title. An alternative links it to Áli, a personal name attested in Scandinavian dynastic legend. The doubling with Loki's son is easier to explain if the word was a descriptive term applied twice rather than a proper name that happened to recur.