Elsa is the fifth spirit, but only because her mother passed the power down through her first child's birth. Elsa cannot be the fifth spirit shown in the forest at the time when her father is still a child. However, Queen Iduna can be.
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.
She died and was reborn to take on her true form like has happened in so many stories before. With that transformation, Frozen 2 has made Elsa an immortal spirit now. Like how Frozen 2's other four spirits appear as animals but more than just that, Elsa still appears human but is more than just that.
Elsa (and Anna, I guess) serves as the bridge between the spirits and the humans. Her ice powers can tame every one of the elemental spirits; ice cools the fire, slows the water and the wind, and I'd assume it can also calm the earth giants, even though that's not explicitly shown in the movie.
The symbolic explanation for why Elsa froze is more straightforward. Elsa freezes in response to the trauma of discovering her family's colonial past. Similar to the plot in Frozen, Elsa is overcome with emotion and loses control of her powers — she is so overwhelmed by her own ice magic that she is literally frozen.
According to Iduna, Ahtohallan is considered a spirit and is the "mother" of all the other spirits. According to Iduna's notes, Ahtohallan is the source of the magic in the Enchanted Forest as well as those of the spirits, including Elsa's powers.
According to Myth: A Frozen Tale, the fifth spirit is also known as the “human spirit”, but it is assumed to have been represented by humanity in general before Elsa and Anna's births. According to Northuldra legend, the spirits' mother is Ahtohallan.
Unbeknownst to Agnarr, Iduna is actually a Northuldran and was the girl that rescued him on the day of his father's death. Because of the kingdom's negative feelings towards the Northuldra, Iduna kept her heritage a secret for many years, though she finally told him everything shortly before their deaths.
It has a slot for November 2024 and November 2025 for “untitled Disney animation”, according to Business Insider. Again, assuming that Frozen 3 is following the same release pattern as its predecessors, it's safe to bet that it will be released November 26, 2025.
Elsa discovered that the call was used by Iduna to summon the Wind Spirit to save Agnarr. Elsa also discovered other memories of her mother, from Elsa's own childhood and those that took place before she was born.
Based on what Anna and Yelena said, it seems Ahtohallan rewarded Iduna's selfless action by granting Elsa with the power to control ice. So basically Ahtohallan had the intention to create a champion for itself, someone who would bridge the two worlds (maybe to prevent another incident?).
Three years later, Elsa is 21 years old and set to be crowned queen. The people of Arendelle are joyously preparing for her coronation day. Anna (now 18) is flushed with excitement as the castle gates are opened for the first time since the sisters' childhood.
Disney's Frozen 2 features Elsa (Idina Menzel) hearing a mysterious voice calling to her throughout the movie, and despite confusion among audiences it has been definitively confirmed it belongs to her mother, Iduna (Evan Rachel Wood).
While Iduna's selfless actions were the reason Elsa was bestowed with ice powers to begin with, her daughter received powers instead of her because beings are born with elemental powers in the Frozen universe and don't acquire them later on in life.
Queen Iduna was the fifth spirit all along and chooses to save King Agnarr knowing that as a royal, she would need to be with him to have her royal daughters. Only by saving Him she is able to be in the position to one day save the enchanted forest through the births of her two daughters.
After her death, Iduna's belongings were stored within the castle passageways. In Frozen: Live at the Hyperion, Iduna briefly returns as a spirit watching over her reunited daughters, during the finale.
Frozen 2 revealed that Elsa is the missing Fifth Spirit, which is the reason for Elsa's powers, but a new theory suggests there are actually Eight Spirits. Frozen 2 delved into the origins of Elsa's powers and why she feels so out of place in Arendelle, despite being close with Anna and the Kingdom once again.
Indeed, as there are no condoms or any other reliable form of birth control in the frontier, there's a real possibility that Ennis really did impregnate Elsa. Sadly, before 1883 could even drop any clues that Elsa was pregnant, Ennis died in the next episode while Elsa died during the finale.
Elsa was also planning to split from the group to stay with Sam, but after many goodbyes, everyone decided they were going to Oregon anyway. Even Elsa decided to leave her boyfriend so she could find out where Oregon was, while planning to return to the plains in June to reunite with him.
The implication, and it's only ever just that, is that Elsa and Anna's mother is herself somehow attuned to the magical forces such that Elsa was given the gift of superpowers. (Why Anna never received such powers is equally vaguely defined: just as Elsa and Anna's father had no powers, so too would she be power-free.
Elysium is the first daughter of Elsa and Jack Frost, protagonists in Frozen and Rise of the Guardians. She is also a Princess of Arendelle and Junior Guardian of Winter. She is the older sister to Elise and is the first heir to the Throne of Arendelle.
While they're in there, Anna and Elsa also discover another twist: They're half-Northuldran. Their mother, it turns out, was a tribe member who saved their father during the battle, escaped with him out of the forest, and later married him.
