Gullinbursti

The Prose Edda tells Gullinbursti's origin as part of a single long episode in which Loki, having cut off Sif's hair as a prank, is forced to make amends by commissioning replacement treasures from the dwarves, and rashly bets his own head against the sons of Ivaldi that no one can outdo the gifts they produce. He turns to the brothers Brokkr and Eitri, who accept the challenge, and Eitri sets a pig's skin in the forge fire and tells Brokkr to work the bellows without stopping no matter what happens, or the working will fail.

Loki, aware he stands to lose the bet and his head with it, transforms into a horsefly and bites Brokkr repeatedly on the hand to break his rhythm, but Brokkr keeps pumping through the pain, and the skin emerges from the fire as Gullinbursti, a boar whose bristles shine gold bright enough to light the darkest road. The same forging session, without pause between pieces, also produces Draupnir, the ring that drips eight equal rings every ninth night, and Mjolnir, Thor's hammer, whose handle comes out shorter than intended because Loki's fly bit Brokkr on the eyelid at the crucial moment, the one flaw in an otherwise unbroken run of treasures.

Once the contest of gifts is judged, with Odin, Thor and Freyr sitting as arbiters, Gullinbursti is given to Freyr alongside Draupnir for Odin and Mjolnir for Thor, and the gods rule that Mjolnir's protective power against giants makes Thor's gift the winning one, so Loki keeps his head only through a technicality about how it may be removed without touching his neck.

Gullinbursti becomes Freyr's mount and, in some tellings, is harnessed to pull his chariot, valued for two qualities beyond his beauty: his golden bristles glow brightly enough to light the way through the darkest night, useful to a god whose domain includes fertility, sunlight and the growing season, and his legs carry him faster than any horse, across land, over water and through the air alike, so that no journey is beyond his reach. Some later folkloric and scholarly commentary connects Gullinbursti to wider Germanic and Scandinavian traditions of the boar as a symbol of fertility and protection in battle, including the boar crested helmets described in Beowulf and other early medieval sources, though the Prose Edda itself ties him specifically and only to this one forging story and to Freyr's subsequent ownership.