Two years after the battle at Sokovia, Thor has been unsuccessfully searching for the Infinity Stones, and is now imprisoned by the fire demon Surtur in Muspelheim. Surtur reveals that Thor's father Odin is no longer on Asgard, and that the realm will soon be destroyed in the prophesied Ragnarök,
once Surtur unites his crown with the Eternal Flame that burns in
Odin's vault. Thor defeats Surtur and claims his crown, believing he has
prevented Ragnarök.
