Hex

Story:
Long ago, Hex was a gifted and powerful sorceress who traveled deep into the underworld to confront the Undead Dragon King named Malefor, who made several attempts to capture her to learn her secrets. Though she successfully battled the dragon, Hex returned from the underworld changed - having unwillingly joined the ranks of the Undead. Many are wary of her since her transformation, suspecting she has used her powerful magic for evil purposes. But Eon trusts her, and views her as a most valuable Skylander ally.

Citation
http://www.skylanders.com/sky/elements/undead/characters/hex