In Frozen 2, the four elemental spirits are behind the deaths of Anna and Elsa's parents, Iduna and Agnarr. The shipwreck, which resulted when the Arendelle rulers were caught in a storm while crossing the Dark Sea on the way to Ahtohallan, was not an accident. The spirits conspire to murder the King and Queen early in Frozen so that Elsa's powers - which were bestowed magically upon her to make her the fifth spirit - could be released and bring balance to nature in the sequel. It isn't just the unruly Kelpie spirit Nokk who is responsible for the deaths of King Agnarr and Queen Iduna, nature itself needs them to be killed for the sake of restoring balance.
Continuing on from the first film's themes of self-discovery and celebrating who you are, throughout Frozen 2, Elsa encounters each of the elemental spirits - along with Anna, Kristoff (Jonathan Groff), Olaf (Josh Gad), and reindeer - on a journey seeking both the source of the voice calling to Elsa and an answer to her own spiritual restlessness. The five intrepid adventurers head North and encounter fire spirit Bruni, wind spirit “Gale,” the Earth Giants, and Nøkk, the water spirit, all of whom Elsa must calm. The spirits' powers are all formidable with each representing a major challenge to Elsa (and Anna in the case of the Earth Giants) and in one thrilling sequence, Elsa battles Nøkk in her attempt to cross the Dark Sea to Ahtohallan.
But what if those powers, which so strongly challenge Elsa in her own quest to uncover the mystery of the siren's song were the intentional cause of the deaths of Agnarr and Iduna? The spirits needed Elsa (and the bridge between her and her sister) to bring true balance to nature and more importantly, they needed her to realize her magical potential to become immortal and follow her true destiny. With her parents standing in the way, that was impossible, so the spirits had to kill the King and Queen.
As Frozen 2's Fifth Element, Elsa Is Supposed To Bring Balance
Elsa is the fifth elemental spirit, and her powers were gifted to her because her mother saved Agnarr as a young boy during the Arendelle army's battle with the Northuldra free folk. Prior to Elsa's birth, Nature itself recognizes the increasing influence and impact of humans on their world - thanks to King Runeard's invasive dam, which weakens not only the Northuldra but also the true course of nature - and gifts Elsa magical powers as a means to restore balance. As Elsa and Anna recognize at the end of Frozen 2, Elsa's status as the fifth element (which was the agenda behind her being empowered) would only work if she was the bridge to the human world. Her influence would make her an envoy of Nature, effectively.
Elsa's relationship with the other four elemental spirits - Nøkk, Gale, Bruni, and the Earth Giants - confirms that her role is one of balance: her first interactions with three of the four are designed to calm them and to bring them back in line. Perfectly balanced in the new alliance of the five spirits that is itself supposed to ensure balance in the elements. When balance is removed, specifically through man's meddling with nature in Frozen 2, the spirits become enraged and chaos reigns because Elsa is not there to bring about balance.
Anna & Elsa's Father Is Suspicious Of Magic (And Wants To Control Elsa's Powers)
Unfortunately for Nature and the four other elemental spirits, they are deceived in their agenda to make Elsa the fifth element by her parents. Thanks to King Runeard's arrogant hatred of magic, which he says "makes people feel too powerful, too entitled" and "makes them think they can defy the will of a king," Agnarr grows up with deep-seated suspicions of magic, which are compounded when Elsa accidentally injures Anna. Both he and Iduna fear the unknown (something they pass on to Elsa) and look for a way to control their daughter's powers. Or better yet, to get rid of them for the greater good.
Terrified for the fate of their daughter, Agnarr and Iduna seek the advice of the troll king, who warned them of dire consequences if Elsa doesn't learn to control her powers, but their understanding of his prophecy is flawed. The troll king is correct that Elsa needs to learn to control her powers, but the dire consequences will come not if she over-uses them, but if she fails to use them for their intended purpose - to bring balance. In their fear, the King and Queen tell Elsa to "conceal, don't feel" her powers and lock her away in the hope of "controlling" her and that is their first fatal mistake, which is all the more tragic because Iduna is Northuldra and should understand the balance of magic and Nature. Their second mistake is taking their journey north.
Why The Spirits Killed Agnarr And Iduna In Frozen
The King and Queen seek their answers in Ahtohallan, but fundamentally, what they're searching for is a way to save Elsa from her powers. They want to rid her and the world of the possibility that something could go wrong if she loses control by finding a solution at the source of her powers and removing them. Aware of their intent, the spirits knew that the fifth element would never get to realize her potential and bring balance back to nature and the solution was to kill Elsa's parents and find a way to fully awaken the new Queen of Arendelle's powers. Consider it this way: if the spirits saw what Iduna and Agnarr were doing as a means to restoring Elsa as the fifth element and bringing balance, why would they have allowed the very things they control - the wind of the storm, the water of the pounding waves, the Earth that cuts a hole in the ship - to kill them? It had to have been a conscious act.
With Agnarr and Iduna out of the way, the spirits drew Elsa to the North not only to show her her destiny as the fifth element but also to help her realize the true limit of her powers. When the spirits attack, they aren't trying to kill her, they're trying to help her control her powers by becoming stronger. As she's able to overcome each challenge, they are "calmed" and Elsa is a little more capable of taking on her responsibilities as the twist that Elsa is the fifth element is revealed. The only somewhat confusing point of contention is the fact that Elsa's mother, Iduna, is the source of the mysterious siren voice that draws her to Ahtohallan. As Frozen 2's co-director Jennifer Lee confirms in Into The Unknown: The Making of Frozen II "the voice is the mother," so the vagueness over that particular issue is settled. If she was killed by the spirits, why does she help them bring her daughter to the North?
Why Elsa's Mother Draws Her North In Frozen 2
The answer to why Iduna would call Elsa to Ahtohallan if she had been killed by the spirits is that she doesn't - at least, not entirely. The siren's call to Elsa is a memory, following a narrative thread that runs all the way through Frozen 2. The pay-off of Olaf saying "water has memory" is not him coming back to life - that would be frivolous in how self-serving it is - but for that idea to be underpinning how and why Elsa is able to hear her mother is a lot more satisfying.
So why did the spirits use Iduna's voice? Well, because Elsa has been taught her entire life to fear the unknown. Key Frozen 2 song "Into The Unknown" is effectively her wrestling with the draw of the mysterious siren song in the North and she only loses her struggle not to "hear" it (as the song opens) because the voice seems so familiar to her. The lyrics see her struggle with that idea of familiarity - "Or are you someone out there who's a little bit like me? Who knows deep down I'm not where I'm meant to be?" - before she finally gives in and tells the voice not to leave her, in a parallel to her real mother leaving her. Her mother becomes something of a totem to her - which is why the spirits show Elsa the image of Iduna saving Agnarr captured in memory - and it is precisely because the voice is not unknown that she is able to convince herself to go "Into The Unknown" in Frozen 2.