Muspelheim
Muspelheim ("Flameland"), also called Muspel (Old Norse Múspellsheimr and Múspell, respectively), is the realm of fire in Norse Mythology. It is home to the fire giants, and their master, Surtr. It is fire and the land to the north, Niflheim is ice. The two mixed and created water from the melting ice in Ginnungagap. Sparks from Muspelheim created the planets, comets and stars.
According to the Ragnarok prophecies in Snorri's Prose Edda, the Sons of Muspel will break the Bifrost bridge, signaling the end of times:
In the midst of this clash and din the heavens are rent in twain, and the sons of Muspel come riding through the opening. Surtr rides first, and before him and after him flames burning fire. He has a very good sword, which shines brighter than the sun. As they ride over Bifrost it breaks to pieces, as has before been stated. The sons of Muspel direct their course to the plain which is called Vigrid.... The sons of Muspel have there effulgent bands alone by themselves.
Reference in popular culture
In the MMORPG World of Warcraft, a dungeon named The Molten Core bears many similarities to the myth of Muspelheim. Molten Core is a dungeon in the theme of fire, placed at the heart of "Blackrock Mountain". Explorers will encounter monsters such as fire giants (named "Molten Giants" and "Molten Destroyers"), fire elementals, flame imps, and at the end of the dungeon, the fire lord Ragnaros awaits, who is the most difficult monster in the dungeon; requiring the coordination and skill of up to 40 players to kill. The name Ragnaros sounds like a play on Ragnarök.