The Ice Queen (Rise of the Guardians/Frozen)

After 10 years Pitch is getting stronger, but the Guardians think that they had defeated him forever, but they were wrong. A spirit sits in her castle high on a frozen mountain on a floating island. Her name is Elsa. No spirit, besides her guards and staff have ever seen her. She stays hidden and rarely comes out of her palace's gates, but when she does she ensures no spirit sees her. Pitch knows about her, but has never seen her and doesn't know where this floating island lies. He has had countless nightmares follow her, but they are never seen again. This is her story