Warning: MAJOR SPOILERS for Frozen 2 ahead.
Elsa and Anna return in Frozen 2, embarking on a journey to find out exactly where Elsa's powers came from - but the movie's ending may leave some confused about the answer to that question. In the new sequel, directed once again by Chris Buck and Jennifer Lee, the kingdom of Arendelle is attacked by mysterious spirits from a nearby enchanted forest, which has been locked away by a magical mist for decades.
With the people of Arendelle evacuated to the mountains, Anna, Elsa, Olaf, Kristoff and Sven head into the enchanted forest to find a way to settle the spirits. Meanwhile, Elsa has been hearing a mysterious siren song that she believes will reveal the truth about her powers. Inside the forest, the group meets the people of Northuldra and some remaining soldiers from Arendelle, who are still at odds over a battle that broke out 36 years ago, angering the forest's spirits and causing the mist to descend. Continuing to follow the siren call, Anna and Elsa discover the wreck of their parents' ship, and learn that they died attempting to cross the Dark Sea to a glacier called Ahtohallan, which holds the secret of Elsa's powers.
Leaving her friends behind, Elsa crosses the Dark Sea to Ahtohallan (with a little help from a kelpie called Nokk), and commands the spirit (in song) to "Show Yourself." She learns that she is actually the fifth spirit of the forest, connecting the other four. She also discovers that her grandfather "gifted" the Northuldra people a dam to weaken their waters, and then ordered an ambush of the Northuldra, killing their leader himself. However, following the memories too deep into Ahtohallan causes Elsa to be frozen like a statue, and her magic dies along with her - which means that Olaf, who is held together by Elsa's magic, disintegrates in Anna's arms.
Fortunately, Anna manages to save the day by figuring out that the dam must be destroyed, and Arendelle sacrificed, in order to appease the spirits and atone for her grandfather's crimes against the Northuldra. She antagonizes the rock giants of the forest so that they chase her to the dam, and then encourages them to fling boulders at it until it breaks. This breaks the spell on Elsa, who recovers in time to race across the Dark Sea on her kelpie and reach Arendelle in time to throw up an ice barrier that saves the kingdom. Frozen 2 gets a typical Disney happy ending - but what did we actually learn about Elsa's powers?
Elsa Is The Fifth Elemental Spirit
Let's delve into the most puzzling aspect of Frozen 2 first: the origin of Elsa's powers, and how she became the fifth spirit of the forest. The simple version is that her ice powers were a gift from the spirits, bestowed on her because of the actions of her mother, Queen Iduna, in saving her father, King Agnarr, during the battle between the people of Arendelle and Northuldra. Shortly before the fighting broke out, Agnarr heard Iduna singing in the forest (the same song that Elsa hears later) and followed the sound of her voice. During the battle he hit his head on a rock and Iduna found him, singing the same song as an apparent appeal to the spirits to help them, and managed to escape the forest with Agnarr before the mist fell.
Iduna didn't have magical powers in the same way that Elsa does, but like the other Northuldra people she had the ability to perform magic by interacting with the spirits of the forest. The teaser trailer for Frozen 2 suggested that she can manipulate the wind to blow leaves around, though this scene didn't make it into the movie (except for a glimpse of it when Elsa enters Ahtohallan). It's possible that an earlier version of Frozen 2 went into more detail about Iduna's life and the exact nature of the spirits, but those elements were ultimately cut.
Just as the spirits punished the soldiers of Northuldra and Arendelle for fighting by wrapping the forest in a magical mist, so too did they reward Iduna and Agnarr's bridging of the divide by giving their daughter powers, imbuing her with the fifth spirit that connects the other four: air, earth, fire, and water. The other four spirits are embodied (respectively) by "Gale" the invisible wind spirit, the rock giants of the forest, adorable fire elemental Bruni, and Nokk the kelpie. As the embodiment of the fifth spirit, Elsa has the ability to tame the other four, which is why she is able to calm Bruni down and catch a ride on Nokk.
Who Was Singing To Elsa?
Elsa being the fifth spirit makes the question of who her "secret siren" is harder to unravel. Though this is somewhat unclear, one possible interpretation resides in Olaf's oft-repeated theory that water has memory. Ahtohallan is the "river of memory" in the lullaby that Iduna used to sing to Anna and Elsa when they were young. The glacier draws water from all around it and crystallizes those memories. When Elsa finally reaches Ahtohallan, the ice cave shows her glimpses of her own past and also of her mother's past, including the moment when Iduna sang over Agnarr. This could mean that the siren call Elsa heard was actually an echo of Iduna that Ahtohallan was using to call to her, so that she could fully realize and accept her powers as the fifth spirit.
Another possible interpretation is that the voice Elsa heard was her own - or at least, the voice of the spirit that resides in her. While Bruni, Gale, Nokk, and the rock giants are the avatars of the elements that they represent, those elements also exist separately from them. Similarly, the glacier of Ahtohallan represents the element of ice, and is therefore a part of the spirit that resides in Elsa. Through her spiritual powers and her unconscious yearning to find out the truth about where they came from, Elsa was effectively calling to herself through Ahtohallan. This theory and the one above are not necessarily mutually exclusive, as Elsa may have been calling to herself using the memory of her mother's voice.
Why Elsa Died & How Anna Brought Her Back
Elsa finding out the truth about Arendelle's attack on Northuldra comes at a cost. The song "All Is Found" carries a warning about Ahtohallan: "Dive down deep into her sound/But not too far or you'll be drowned." After finding out that she is the fifth spirit and her grandfather ambushed the people of the forest, Elsa continues to follow the ghostly soldiers until she reaches a great pit. This is the point at which she should have turned back, but instead she decides to jump into the pit to follow them - at which point she becomes overwhelmed by the memories and turns to ice. This represents the overall theme of Frozen 2: you have to acknowledge the sins of the past to undo the damage they've done, but dwelling in the past too much will leave you stuck in it.
The people of Northuldra and the Arendelle soldiers remaining in this forest also have to learn this lesson. For 36 years they have maintained their animosity towards one another, and they are still at odds when Elsa and the others arrive. The only way to end their fight and appease the spirits is to actually undo Arendelle's crimes, rather than simply reliving them like Elsa does. Anna achieves this by convincing Lieutenant Mattias that the dam must be destroyed, even if it means destroying Arendelle in the process. The spirits, who were angered by the building of the dam and the subsequent fighting, are satisfied by the balance being restored, and their powers come together to revive Elsa, who in turn saves Arendelle (and brings Olaf back).
Why Anna Becomes Queen & What Happens Next
A big question that fans may have about Frozen 2 is why only Elsa was given ice powers and became the fifth spirit, whereas Anna is normal. It's explained that the two sisters represent the two sides of a bridge and, in turn, the two kingdoms of Northuldra and Arendelle. Since Elsa is more closely linked to her mother's side of the family and the enchanted forest, she realizes that she truly belongs with the Northuldra, and abdicates the throne of Arendelle. Anna, signifying the other half of the bridge and their father's family, becomes the new Queen of Arendelle, while Elsa goes to live in the forest. A statue of their mother and father as children is unveiled, symbolizing the newfound peace between Arendelle and Northuldra.
Assuming Frozen 2 performs well enough at the box office for Disney to go ahead with a sequel (and it looks like it definitely will), the next adventure could go in a number of directions. Frozen 2 was somewhat unusual in that it didn't have a villain, and was more a journey of self-discovery. However, the movie did go out of its way to repeatedly remind the audience of Frozen's villain, Prince Hans, so it's possible that we'll see him return with a vengeance in the future. Now that Anna is ruling over Arendelle and Elsa is watching over the forest, they should be ready for whatever future troubles come their way.