Which Norse god is the guardian of the rainbow bridge Bifröst?

Heimdallr is the Norse god who guards the rainbow bridge Bifröst.

Heimdallr serves as the watchman of the gods, stationed at Himinbjörg, the dwelling associated with the point where Bifröst reaches the heavens. His duty is to watch for invaders and detect the coming of Ragnarök. The Prose Edda gives him extraordinary senses: he can see exceptionally far, see at night as clearly as during the day, and hear remarkably faint sounds.

His main signal is Gjallarhorn, a resounding horn whose blast announces danger and, in the Ragnarök story, the final crisis facing the gods. He also owns the golden-maned horse Gulltoppr and is described by titles including “guardian of the gods,” “white god,” and “son of nine mothers.”

Heimdallr is sometimes confused with a generic bridge keeper from modern fantasy, but the surviving myths give him a much larger role. He is a divine sentry, a possessor of hidden knowledge, and an enemy of Loki. At Ragnarök, the two are prophesied to kill one another, making Heimdallr central to the myth’s concluding battle.