In Scandinavian mythology, Asgard is a heavenly realm ruled by Odin, the supreme deity and creator.

It is inhabited by the Norse gods known as the Aesir, one of the two main tribes of deities venerated by the Norse. Some of these gods are Odin and Frigg, his Queen; Thor, the master of Mjolner; Balder, the good; the one-handed Tyr; Brage, the songsmith; Idun, the goddess of youth; and Heimdal, the watcher of Asgard.

Asgard contains the great hall known as Valhalla (“Hall of the Dead Heroes”), the abode of heroes slain in earthly battle, and is separated from Jotunheim (the land of the giants) below it and the place of the gods known as the Vanir, by a bridge, Bifrost, guarded by the watchman Heimdall.

Valhalla, presided over by the high god Odin, is described as a palatial hall built with shields and spears and contains 540 doors.

Valhalla is where the fallen warriors put on armor each morning and fight each other to the death. Rising again, the warriors drink and feast on a boar slaughtered daily and made whole again each evening. When Ragnarok (“Doom of the Gods”) arrives, 800 warriors will march out of each door to fight the wolf Fenrir and fight alongside Odin against the giants.

Chapter 5 of the Prose Edda, a text describing Norse beliefs and mythologies produced around 1200 CE by the Icelandic poet Snorri Sturlson (1179-1241), describes Odin and offers a description of the realm of Asgard in which Valhalla is located,

There [Asgard] dwelt the gods and their race, and thence were wrought many tidings and adventures, both on earth and in the sky. In Asgard is a place called Hlidskjalf [Valhalla], and when Odin seated himself there in the high−seat, he saw over the whole world, and what every man was doing, and he knew all things that he saw. His wife hight Frigg, and she was the daughter of Fjorgvin, and from their offspring are descended the race that we call asas [Aesir], who inhabited Asgard the old and the realms that lie about it, and all that race are known to be gods. And for this reason Odin is called Alfather, that he is the father of all gods and men, and of all things that were made by him and by his might.