Bifrost

Bifrost, also spelled Bifröst, is a central element of Norse mythology. It denotes the rainbow bridge that connects Asgard, the realm of the Æsir, with Midgard, the world inhabited by humans. Descriptions portray it as a blazing, multicolored bridge spanning the cosmological distances, visible across the heavens.

The bridge is guarded by Heimdall, the watchman of Asgard, who stands at its far end and is known to blow the Gjallarhorn to warn the gods of danger. Crossing the Bifrost is typically a task reserved for those who serve the gods or are granted permission for travel between realms. In various sources, the bridge is described as fragile or under threat, and it is commonly said to be destroyed or broken during Ragnarök, the cataclysmic end of the world in Norse myth.

In modern culture, Bifrost has been adopted as a symbol of cosmic travel and interrealm gateways. It appears in comics, films, and video games, most famously in the Marvel Comics and Marvel Cinematic Universe, where Bifrost is portrayed as a portal network or gateway enabling rapid travel between realms, often associated with the realm of Asgard and overseen by Heimdall. The concept remains a marker of crossing between the divine and mortal worlds in various adaptions.