Thor: The Dark World (2013)

Asgardian king Odin (Anthony Hopkins) reveals that before the birth of light, there was darkness. From that darkness came the Dark Elves of Svartalfheim, led by the evil Malekith (Christopher Eccleston). Malekith sought to use the powerful Aether to plunge the universe back into eternal darkness, but the Dark Elves were defeated by Odin's father Bor and his Asgardian army. Malekith and his friend Algrim (Adewale Akinnouye-Agbaje) escaped with the remaining Dark Elves. Bor and his army subsequently buried the Aether hoping it would never be found.

On Asgard in 2013, evil God of Mischief Loki Laufeyson/Odinson (Tom Hiddleston) stands trial for his crimes in the first film and the Battle of New York in the first Avengers film, in which Loki took many human lives. Loki feels no remorse for his evil actions and claims it his birthright to rule Asgard. Odin tells Loki his birthright was to die as a child when evil Frost Giant king Laufey (Colm Feore) cast him out onto a frozen rock on Jotunheim. Odin also tells Loki Frigga (Rene Russo) is the only reason Odin is sparing his life and Loki will never see her again and will spend the rest of his days in the Asgardian dungeon and that Thor will be king after he undoes the damage Loki has done and has subsequently brought peace and order to the Nine Realms.

On Vanaheim, God of Thunder Thor (Chris Hemsworth) battles an army of Marauders who are trying to conquer the Nine Realms after being inspired by Loki's evil actions. Beautiful Lady Sif (Jaimie Alexander) also battles the Marauders alongside Thor and the Warriors Three. After they defeat the Marauders, Bifrost gatekeeper Heimdall (Idris Elba) opens the Bifrost portal and Thor, Sif, and the Warriors Three return to Asgard with the arrested Marauders. The Marauders are thrown in the dungeon in cells next to Loki's. While the Marauders are forced to stand or sit on the floor in their empty cells, Loki's cell has blue luxurious furniture inside, including a bed, a table and chair for Loki to read the books Frigga supplies him with, and also a table with food and drinks for him. This is because Loki is part of the Asgardian Royal Family. Meanwhile, on Earth, Jane Foster (Natalie Portman) finds the Aether, which goes inside of her. Thor takes Jane to Odin on Asgard and they try to figure out a way to extract the Aether from Jane.

On Svartalfheim, Malekith and Algrim are awakened by the power of the Aether and realise it is on Asgard. As part of their evil plan to recapture the Aether, Algrim allows the Warriors Three to capture him and lock him in the dungeon with other Marauders while Malekith plans an invasion of Asgard with his army of Dark Elves. Frigga visits Loki in his cell via magical projection and tries to get Loki to take responsibility for his crimes but Loki refuses, angrily declaring Odin is not his father and Frigga is not his mother, after which Frigga's projection sadly vanishes. While Loki lies on his bed throwing and catching an ornament, Algrim pulls a magic stone from his armor that Malekith gave him, and transforms into a dangerous Kurse monster. Kurse kills the inmates in his cell and breaks out of his cell, killing two Asgardian guards. Kurse starts a dungeon breakout by freeing all the Marauders from their cells. Kurse stops by Loki's cell and sees Loki smiling evilly at him, assuming Kurse will free him too. However, Kurse quietly realises Loki is too dangerous and unpredictable and decides not to free Loki. It is also possible Kurse may realise Loki is part of the Asgardian Royal Family after seeing the blue luxurious furniture in his cell, given that all the other cells were empty. Loki puts his family in danger by giving Kurse directions to the palace, telling him to take the stairs to the left.

Thanks to Loki, Kurse destroys the palace's protective shield, allowing Malekith and the Dark Elves entry into the palace, after which Malekith and Kurse kill Frigga when she tries to protect Jane from them. Thor, having painfully witnessed his mother's death, blasts Malekith in the face with lightning from Mjolnir. Malekith and Kurse escape Asgard without the Aether. After Frigga's funeral, Thor plots with Heimdall, Lady Sif, and the Warriors Three to take Jane to Svartalfheim in order to prevent Malekith from attacking Asgard again. Thor is going to need Loki's help, as Loki is the only one who knows of a secret portal to Svartalfheim. Loki has trashed his cell in a rage over Frigga's death, which he is partly responsible for. Thor promises Loki vengeance against Malekith for killing their mother in exchange for safe passage to Svartalfheim. Thor, Sif, and the Warriors Three threaten to kill Loki if he betrays Thor. While Sif and the Warriors Three hold off Odin's guards, Loki takes Thor and Jane to Svartalfheim. Loki seems to betray Thor by stabbing Thor, kicking Thor in the head, and cutting off Thor's hand in front of Malekith.

Loki throws Jane on the ground, proclaiming his allegiance with Malekith and his desire to watch Asgard burn. While still not trusting Loki, Kurse tells Malekith Loki is an enemy of Asgard, since he was a prisoner in the dungeon. After Malekith extracts the Aether from Jane, Loki reveals his betrayal was an illusion, restoring Thor's hand. While Loki shields Jane, Thor uses lightning from Mjolnir to destroy the Aether but fails. Malekith absorbs the Aether into himself, gaining more power. Thor and Loki battle Kurse and other Dark Elves while Malekith escapes on his spaceship. Loki stabs Kurse with a huge blade, but Kurse impales Loki on the blade. While Loki lies on the ground, he reveals he activated one of Kurse's death portals, which destroys Kurse from the inside out, making him disappear. Loki fakes his death in Thor's arms, causing Thor to grieve for him.

After Thor and Jane leave Svartalfheim, Loki kills one of Odin's guards, shape-shifts into the guard and returns to Asgard and banishes Odin from Asgard, subsequently taking Odin's form and ruling Asgard. On Earth, Thor battles Malekith. The Aether's power causes them to fight in London, on Svartalfheim, and on Jotunheim, unleashing a Jotun Beast in London, where the Jotun Beast eats one of the Dark Elves. Thor eventually extracts the Aether from Malekith, and Malekith is killed on Svartalfheim when his ship falls on top of him, crushing him. Thor returns to Asgard and tells "Odin" he doesn't want the throne. After Thor leaves, Loki returns to his true form on the throne, happy that he is now king instead of Thor. The Jotun Beast is still running loose in London. In a post credits scene, Lady Sif and the Warriors Three give the Aether to the Collector.