9. Muspelheim
This is the home of the Demons ruled by Surtur. Muspelheim is like how Hell is often depicted; a realm of eternal fire. If Muspelheim is Hell, then Surtur is the Devil; an enormous fire demon of pure malevolence who want to burn all of the nine realms. It has practically been confirmed that fire demons from Muspelheim will appear in The Dark World. In part of the casting call, Marvel requested men skilled in fire twirling and fire breathing. In the same storyline from the comics, when Malekith shattered The Casket of Ancient Winters, Surtur sends his fire demons to invade Earth and then he himself attacks Asgard. It is likely that The Eternal Flame, also contained in Odin's Vault, will be used by Surtur to enchant his sword and increase his power. In The Dark World, we will get to see Malekith and his Dark Elves and Surtur and his fire demons fighting Thor and his heroes. It is likely that this battle will have repurcussions for all of the nine realms, and we may see the Light Elves, dwarves, trolls and ogres all joining in the fight against this threat. No doubt Loki will have a hand in all of this too.