Muspelheim is a dyson sphere and one of the Nine Realms.
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During the Convergence of 2013, Muspelheim was one of the realms that could be seen from Earth during the Battle of Greenwich. As the Convergence went underway, Malekith attempted to use the power of the Aether to turn Muspelheim and all the other Nine Realms into complete darkness, until he was stopped and killed by Thor before the end of the Convergence.
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- In the non-canon video game Thor: God of Thunder, Muspelheim was the home of the Fire Demons, and considered to be the most dangerous of all, its hellish environment being hazardous even to Asgardians.
- In Norse Mythology, Muspelheim is the primordial realm of fire, light, and heat whose flames combined with the rime flows of Niflheim to form water which the gods used to create all of Midgard.