Gullinbursti is a boar in Norse mythology that served as the steed of Freyr. It was made to be able to run through air and water better than any horse, and its glow would help light the way no matter how dark it became.
Gullinbursti was created by the dwarf Sindri as part of a contest between him and his brother Brokkr, to determine which of them could craft superior gifts for the Aesir. However, Loki, who convinced the brothers to compete against the sons of a dwarf named Ivaldi, shape-shifted into the form of a bloodsucking fly and stung Sindri several times while Sindri was working, but Loki was unable to fully stop Sindri and Brokkr from creating Gullinbursti and the self-replicating ring Draupnir, although the handle of Mjolnir was shorter than what the brothers would have preferred.