Queen Iduna

May contain spoilers for Frozen II(Trust me people, there are plot twists.)"'Agnarr, I'm here. I'm here for you. And if I know one thing it's that you and I will always find a way!'"

One account of her history:
Iduna was a young warrior who was part of the Northuldra tribe which lives in the Enchanted forest. (Yes, that means your favorite ice queen and her sister is half Northuldran... I told you there were spoilers.)

The Northuldra made an alliance with Arendelle, and the King of Arendelle at the time, King Runeard who was also Prince Agnarr's father, gave them a "gift of peace" by building a dam which turned out to be sabotage.

While Agnarr and the accompanying Royal Guard were enjoying festivities together with the Northuldra to celebrate the dam, Runeard assassinates their chief. Thus, causing chaos.

The warriors started clashing weapons with the Royal Guard, but it was their number 1 priority to protect the heir to the throne, which was Agnarr. But Runeard, (In the sweet, sweet taste of karma) was pushed off a cliff by a Northuldran warrior.

Something (which I don't know what, I ain't the all knowing Grand Pabbie.) kept the guards occupied, so Agnarr was knocked out and left alone. (Now this is where Iduna comes in.) Iduna discovers him, but instead of killing him, she saves him, and escapes with him to Arendelle. (OoOOHh, LoVe sToRyY.) The two become best friends, and they grew closer in Agnarr's first few years of kingship, then they get married and have two children. The first is Elsa, then Anna 3 years later. They unfortunately die in a storm on the Dark Sea, trying to find the secret to Elsa's power. (Seriously, what is with Disney and orphaned princesses!?)

Films:

She doesn't have a noticeably big part in Frozen, but her lullaby in the flashback at Frozen 2 lay the foundation of the entire movie.