After the events of the Avengers, Thor returns to Asgard, where Loki has been imprisoned for his crimes. But Loki has secretly learned that Ragnarok is approaching and escapes, believing the prophecy can be used to destroy Thor and Odin. Meanwhile, Thor confronts Ulik and discovers that an army of fire demons led by Surtur is preparing to invade Earth. Captain America and Iron Man join Thor in battle, while the mysterious Beta Ray Bill arrives and eventually fights alongside them.
Loki intends to exploit Surtur’s arrival by controlling the fire demon and using him to eliminate Thor and Odin. But Surtur cannot be controlled. Using the chaos created by his army, he reaches the Bifrost and travels to Asgard. Thor attempts to stop him but is overwhelmed, forcing Odin to confront Surtur himself. In a final battle, Odin kills the demon but sacrifices his own life in the process.
With Ragnarok now inevitable, Thor confronts Loki and defeats him, choosing not to kill his brother but cutting off his head and leaving him alive. Thor then realizes that saving Asgard does not mean saving the city itself. To prevent Ragnarok from killing his people, he destroys Asgard and removes it from Yggdrasil, sacrificing the realm to save the Asgardians. As the great kingdom falls, Thor accepts his new role as the protector of its surviving people.
Post-credit scene: A ship carrying the surviving Asgardians descends toward Earth and lands in Oklahoma. Thor looks across the unfamiliar landscape as the refugees begin building a new home.
