Queen Iduna ruled alongside her husband, King Agnarr. Of the two monarchs, Iduna appears to be far more passive, gentle, and openly emotional than her husband, though with the crucial motherly nature needed to raise Anna and Elsa. The novel A Frozen Heart shows that Iduna was something of a peacekeeper in the household, as whenever Agnarr would lose his temper, Iduna was able to calm his nerves. This carried over to other occasions, such as Elsa's training to control her powers; the queen was an advocate for momentary breaks, in hopes of preventing Elsa from becoming overwhelmed.
The Queen's name was not in the film's credits but is seen written in the Runic alphabet on their memorial stone markers. According to those, the name of the queen is Iðunn (English: Idun/Iduna). However, this was not been confirmed by the filmmakers.
- The Queen's Name: Iðunn can be anglicized as Ithunn or Idunn/Idun. Iðunn means 'youthful', 'eternal youth' 'again to love'. The name Idun is a popular name in Scandinavia, the setting of Frozen. The name Idun also means 'rejuvenation'.
Iduna first appears after Elsa accidentally strikes Anna in the head with magic. Iduna rushes into the room alongside Agnarr, and fearfully comments on Anna's low temperature. Agnarr uncovers a map that leads to the Valley of the Living Rock, home to Grand Pabbie and the trolls. Grand Pabbie is able to heal Anna, who remains fast asleep in Iduna's arms throughout the entire meeting. Before departing, Pabbie explains that Elsa must learn to control her powers. Agnarr ensures that his daughters and the kingdom will be safe by closing the castle gates, limiting Elsa's contact with people, and keeping her powers hidden from everyone—including Anna.
Over the years, Iduna and her husband assist Elsa in controlling her abilities, though most attempts are unsuccessful. When Agnarr tries to comfort his daughter during a mild panic attack, Elsa recoils and demands not to be touch, which nearly brings the Queen to tears. Several years later, Iduna and Agnarr leave for a two-week voyage at sea. In during which, they are caught in a maelstrom and are lost to the ocean depths. In Arendelle, a funeral is held in honor of the monarchs (which Elsa does not attend). Iduna is last seen through a portrait of herself and Agnarr as Kai and another servant drape over it.
Iduna and Agnarr briefly appear in Elsa's flashback during the reprise of "Ring in the Season". When Anna asks Elsa if their family has any holiday traditions, the only instance that Elsa could recall was the annual ringing of the Yule bell, although Anna pointed out that the Yule bell ceremony was more for the kingdom, rather than something personal to their family.
The Queen appears in live-action form in the first episode of the fourth season, which has the backstory of the events happening in Arendelle prior to Frozen. Here, she is called Gerda (a character named "Gerda" does appear in Frozen, but she is one of the servants, not Elsa and Anna's mother).
Ingrid fears hurting her sisters with her powers, but her sisters promise to help conceal the powers and continue to sustain their unity. Years later, on the night of their father's birthday celebration, Gerda and Helga attempt to convince Ingrid into coming with them, but her fear of ruining the party overshadows her sisters' pleads. At the party, Helga introduces a new admirer, the Duke of Weselton, to their father.
After the party, the sisters arrive home to find Ingrid packing up as she believes with herself gone, they can have normal lives, fearing she won't be able to control her powers. Gerda mentions Rumplestiltskin, who may help. In exchange for their ribbons (which the sisters used to symbolize their sisterhood), Rumplestiltskin gives Ingrid a pair of gloves to conceal her powers, as well as an urn to entrap her if she becomes too dangerous. Later, in the royal garden, Gerda comes across Ingrid crying over the frozen and crumbled body of Helga. Realizing Ingrid, whether intentionally or not, killed Helga, Gerda entraps her in the urn. She then seeks out Grand Pabbie and asks him to erase her sisters' existences from everyone's memories, even though he implies a magical price will be extracted at her expense.
After marrying her husband, they rule as Queen and King of Arendelle and give birth to Elsa and Anna. When Elsa exhibits powerful and dangerous ice powers, the couple travels to the nearby land of Misthaven to find a wizard to get rid of her magic. On the return trip home, the ship is caught in a maelstrom. Realizing they might not make it out alive, Gerda hastily writes a note, places it into a bottle and throws it overboard in the hopes Elsa and Anna will find it. Soon after, the ship capsizes and sinks, drowning them.
Gerda's message winds up on the beach of Storybrooke 35 years later. A recently thawed out Anna finds the note and brings it to the Snow Queen's cave. There she reads it to Ingrid, Emma, and Elsa. It explains that the couple was wrong to keep the two girls apart and to hide Elsa from the world. Gerda also explains that she feels guilty about what she did to Ingrid and wishes that she could take what she did back.
- Iduna's character model, upon closer look, is simply a recolored and customized version of Elsa's coronation appearance, such as her wearing her hair in a crown-twist bun (only with brunette hair instead of platinum blonde). There have been several differences, including her clothing and dark brown hair, and her face is thinner than both of her daughters, but her face and eyes resemble both girls.
- In Once Upon a Time, Iduna's name is Gerda, which was the original name of the heroine in the original "Snow Queen" fairy tale, who was the inspiration for her daughter Anna.
- According to the read-a-long book "Anna and Elsa's Winter End Festival", the queen had quite a sweet tooth and believed in fresh air and exercise. Her birthday is said to be "at the end of winter, right before spring."
- 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.
- In the film, the only thing Iduna says is "She's ice cold."
- Iduna's sole line was recorded by Jennifer Lee, the films co-director and screenwriter. Coincidentally, Lee's daughter, Agatha, voiced 9-year old Anna.