The Ice Castle was created by Elsa as practice for her powers on the North Mountain a day's walk away from Arendelle.
The entire palace is centered around the hexagonal shape of a snowflake. A "flawless" staircase leads to double doors which can open by themselves into the palace. The first room has a beautiful frozen ice fountain and two curving staircases along the sides which join together on a platform above and across from the entrance. Another curving staircase branches off from the platform up into the "heart" of the palace. This is the room with a grand ice chandelier and Elsa's signature snowflake where the floor and walls change color to match Elsa's emotions, much like a mood ring: blue when happy, purple when sad, red when frightened, and amber when angry (which may just be the reflection of the sunlight in the ice)
After Elsa was found out about her powers infront of the entire kingdom, Elsa ran across the docks to the mountains. There she began to practice her powers as a means of "letting go", creating Olaf, the icy staircase and the castle it led to. There she finds refuge from the world, intending to live the rest of her life in solitude.
Olaf leads Anna, Kristoff and Sven to Elsa and the ice palace at their request. Anna pleads her sister to come back home with her to restore summer to Arendelle together. Upon learning of the eternal winter Elsa caused even all the way up in her palace, she becomes distressed and her powers explode out, striking Anna in the heart. Anna still refuses to leave Elsa, and to protect her from further harm Elsa creates Marshmallow to throw Anna and Kristoff out.
Later on, Hans, the Duke's henchmen and other soldiers arrive at the ice palace searching for Anna. Hans orders "No harm shall befall the Queen" but Marshmallow roars at the intruders and a fight commences. With the distraction, the thugs go after Elsa, defying Hans' orders and following the Duke's. Hans slices Marshmallow's leg off, causing the snowman to lose his balance and fall off the mountain where his claw breaks Elsa's staircase and almost makes Hans fall to his death.
Meanwhile, the thugs chase Elsa up to the snowflake room which is glowing amber. Frightened, Elsa talks to the thugs as they aim their crossbows at her, "Please. No." Elsa freezes an arrow inches from her face, reluctantly beginning to use her powers in defense. The tables turn and Elsa threatens both men's lives. And it doesn't seem like she intends to stop. Hans and the rest of the search party enter the room then, and Hans implores, "Queen Elsa! Don't be the monster they fear you are!" Stunned, Elsa stops, allowing the time for one of the guards to aim his crossbow at her. Hans sees this and runs, deflecting the crossbow up where the arrow slices the ice chandelier and falls. Elsa manages to run away before it crashes on her but she still gets knocked out and is taken with the party back to Arendelle.
Role in the CrossoverEdit
The Ice Castle serves as both a second-home to Elsa and a noticable beacon (both magical and architectural), serving as a meeting place for Elsa and characters of the more magical variety (mainly Jack Frost). Otherwise, Elsa would meet them in Arendelle Castle or in other locations.