Thor is imprisoned on the fire-demon world of Muspelheim, where he is held captive by Surtur, a monstrous entity who prophesies the coming of Ragnarök—the destruction of Asgard. While chained in a cavern, Thor learns that Odin is no longer on the throne and that Asgard has been left unprotected. Surtur reveals that Odin’s absence has allowed the conditions for prophecy to unfold, as the Eternal Flame within Odin’s Vault can restore Surtur to his full power if his crown is united with it. Realizing the danger, Thor defeats Surtur’s minions and escapes, taking Surtur’s crown with him in hopes of preventing catastrophe.

Thor returns to Asgard to discover that Heimdall has been declared a fugitive and replaced by the opportunistic Skurge. Heimdall is in hiding, secretly aiding the population, while Skurge reluctantly allows Thor passage. Thor and Loki confront what appears to be Odin on Earth, only to uncover Loki’s deception. They locate the real Odin in Norway, where he is in his final days. Odin reveals a devastating truth: Hela, the Goddess of Death and the long-lost firstborn of Asgard, will be released upon his death. With his passing, Hela immediately emerges from imprisonment, confirming his warning.

Hela quickly asserts dominance, revealing her immense strength and connection to Asgard’s history. She shatters Mjolnir effortlessly, overpowers both Thor and Loki, and kills the Warriors Three and Asgardian forces that resist her. During their escape attempt, Hela intercepts them on the Bifrost and forces them into space. Loki and Thor are separated, with Loki later landing on Sakaar and ingratiating himself with the planet’s ruler, the Grandmaster, while Thor is lost in a wormhole.

Thor crash-lands on Sakaar, a chaotic junkyard planet filled with debris from countless worlds. He is captured by scavengers and eventually brought before the Grandmaster, who recognizes him as a potential asset in his gladiatorial arena. Thor is forced into combat and soon discovers that the Grandmaster’s champion is the Hulk, who has been trapped in gladiator form for years. Thor attempts to reason with Bruce Banner within the Hulk, but the battle intensifies until the Grandmaster manipulates the outcome, ensuring Hulk’s victory.

Imprisoned in Sakaar’s gladiator quarters, Thor meets Korg, Miek, and later reconnects with Loki and Valkyrie, a former Asgardian warrior who has become a bounty hunter. Valkyrie initially refuses to return to Asgard, haunted by memories of Hela’s massacre of the Valkyries. Thor learns that Hulk has suppressed Bruce Banner since Sokovia, and after triggering Banner’s return through a recording of Natasha Romanoff, the two finally regain communication.

Thor, Valkyrie, and Banner form an uneasy alliance and attempt escape using the Grandmaster’s ship. Loki briefly betrays them but is subdued, and Valkyrie ultimately chooses to help after confronting her past. The group ignites a rebellion among Sakaar’s slaves and gladiators, steals a ship, and escapes through a massive interdimensional portal known as the “Devil’s Anus,” heading back toward Asgard.

Meanwhile, Hela establishes her rule over Asgard, reviving the ancient undead army through the Eternal Flame and summoning her massive wolf, Fenris. She enforces her reign through fear, executing resistance and appointing Skurge as her executioner. Heimdall secretly leads surviving Asgardians to safety, preparing for evacuation as Hela’s forces tighten control.

Thor and his allies return to Asgard to find Hela’s rule fully entrenched. A large-scale battle erupts across the realm. Hulk battles Fenris, Valkyrie protects fleeing civilians, and Loki arrives with reinforcements from Sakaar. Despite their efforts, Hela remains overwhelmingly powerful. Thor is severely injured in combat, losing his right eye.

During a vision, Odin appears to Thor and reveals that Mjolnir was never the source of his power—his strength has always come from within. Embracing this truth, Thor unlocks his full lightning abilities. At the same time, Skurge redeems himself by sacrificing his life to save civilians. Loki retrieves Surtur’s crown from Odin’s Vault, realizing the only way to stop Hela is to fulfill Ragnarök.

Thor and Loki agree to unleash Surtur, placing the crown into the Eternal Flame and resurrecting him at full power. Surtur rises as a colossal force of destruction, and Asgard begins to collapse. Thor, Valkyrie, and the survivors evacuate on a ship while Hela attempts to stop them. In the ensuing destruction, Surtur destroys Asgard entirely, killing Hela and fulfilling the prophecy.

With Asgard gone, Thor accepts that his people—not the physical realm—are what define his kingdom. He reconciles with Loki, acknowledges Valkyrie’s leadership role, and leads the surviving Asgardians toward a new future on Earth. As they journey through space, an enormous unidentified ship appears ahead of them, signaling a new threat on the horizon. In Sakaar, the Grandmaster faces a rebellion from his former subjects, unsuccessfully attempting to declare the uprising a “draw.”