Muspelheim

One of the two primordial realms, Muspelheim - or Múspellsheimr in Old Norse - is a dangerous land of fire, heat, and light. It was not created by the gods like most other realms and its exact origin cannot be traced; it simply was. Along with the other primordial realm, Niflheim, Muspelheim is responsible for the creation of the first being in the universe - the giant Ymir. Ymir then created the first jotuns, and was eventually slain by the Aesir. His body was used to create the other nine worlds.

Much like the fiery image of "Hell" that Christian mythology inspires, Muspelheim is a world set ablaze. Not much can be found there besides flames, lava, and soot. This does not mean it isn't inhabited, however, as it is home to the fire giants. These beings are the only things said to be able to survive the realm’s conditions; as the infamous Snorri Sturluson put it, "It is light and hot...that region flames and burns so that those who do not belong to it cannot endure it." This host of giants and demons is led by their king, Surtr, who will lead them en masse to fight against the gods at Ragnarok; at which point he will use his giant flaming sword to destroy Asgard.