Suddenly, in the middle of the night, Elsa wakes up when she hears the mysterious voice calling to her again. Unable to ignore it this time, Elsa tries to follow the voice "Into the Unknown", but unintentionally awakens the elemental spirits, forcing everyone in the kingdom to evacuate as many of Arendelle's resources are stripped from the kingdom: The waterfall dries up, as do the fountains, the flames providing light in buildings and the street lamps are extinguished, the wind becomes fierce, and the streets are disrupted like something is burrowing beneath them and disturbing the earth underneath. Grand Pabbie, the leader of the trolls, senses danger and arrives in Arendelle with the rest of the trolls. Pabbie informs Anna and Elsa that they must set things right by discovering the truth about the kingdom's past, or he foresees no future for Arendelle. Deducing she must follow the voice she has been hearing, Elsa tries to tell her sister that she must go alone, but Anna insists upon coming with her. As Elsa tries to reason with her sister, Anna says she went through many odds three years ago such as climbing the North Mountain, surviving a frozen heart, and saving Elsa from the evil Hans, which in Anna's opinion, is the reason why she's going. Elsa had asked to borrow Kristoff's wagon and Sven, which he did not feel comfortable with. After Anna states that she is coming, Kristoff agrees, insisting on driving. Olaf agrees, adding, "I'll bring the snacks!" Pabbie promises to look after the people of Arendelle in the meantime until the royal sisters return from pacifying the elemental spirits and restoring Arendelle's resources once the spirits are no longer angry for the previous transgression against them. However, Pabbie speaks to Anna in private, voicing his concern about how they always feared Elsa's powers were too much for the world, but now, they are praying they are enough to help save Arendelle. Understanding the meaning of his words, Anna promises to look after Elsa and keep her safe, swearing "I won't let anything happen to her."
With Anna and Olaf safe as far as she knows, Elsa encounters the Nokk, the water spirit who guards the ocean in the form of a glistening stallion, on her way to Ahtohallan. After a fierce fight with the Nokk trying to drown her before reaching Ahtohallan, Elsa tames the Nokk and finally reaches Ahtohallan. Elsa discovers that the voice was the call of Iduna from memories of the past, as an image of her singing her mysterious call to an unconscious Agnarr after saving him flashes onto the wall. Elsa discovers that her power was a gift from the magic of nature, due to Iduna's selfless act of saving Agnarr when the Northuldra and Arendellians starting fighting and the elemental spirits turned against humanity. This makes Elsa the fifth spirit, a bridge between humans and nature, who unites differences. Elsa wields her mother's mantle of the fifth spirit and asks the voice to "Show Yourself". She also learns through flashbacks and memories that the dam was built as a ruse to reduce the Northuldra's resources, due to Runeard's dislike of the tribe's connection with magic, believing it gives them a reason to defy royalty like himself, much to Elsa's chagrin as she realizes Runeard let his fear control his actions, while she learned fear is what can't be trusted. Elsa learns that King Runeard, although depicted as good, was the one who initiated the conflict with the Northuldra. Elsa sends this information to Anna. However, as she had ventured into the most dangerous part of Ahtohallan and ignored her mother's warnings, Elsa becomes frozen herself, turning to solid ice in a more slow, painful version of what happened to Anna under the frozen heart curse, entombing her in Ahtohallan as her grave as she sends the truth to Anna before taking her last breath. Olaf, being made of Elsa's now-defunct magic, fades away and becomes a pile of snow. Anna is left devastated and alone by the loss of her sister and Olaf. She feels that her life is over and that she must give up, but she convinces herself to do "The Next Right Thing" and continue. 781b155fdc