Muspelheim is the realm of fire, lava, and smoke. The only inhabitants that we know of are the fire giants, who stand under the command of Surtr. Muspelheim and its inhabitants already existed before the first gods came into existence. This sets the fire giants apart from all other giants, as they already existed before the primordial giant Ymir came into being. The fire giants are known as the Sons of Muspel, possibly indicating that they are the descendants of another primordial being that we have never met.

Muspelheim would be both the beginning and the end of the universe. It was the heat of Muspelheim that had melted the ice of Niflheim, so that Ymir could rise from Ginnungagap, ultimately enabling the creation of the universe. It would be Surtr and his fire that giants that destroy the universe during Ragnarok.

The stars that we see when looking at the sky at night, are sparks that flow from the realm of Muspelheim.