Sophia

Sophia of Tír-Mòr (Simply known as Sophia) was a young sidhe who was exiled from Avalon, the land of eternal youth, when her father Aulfric killed another sidhe.

Biography
The pair were forced out of Avalon and given mortal bodies. However they were allowed to maintain their magic powers. Aulfric wished to allow Sophia access to return to Avalon and convinced her to enchant Arthur Pendragon so that they might sacrifice him to the sidhe, who required the soul of a mortal prince. When the ceremony began Aulfric revealed to Sophia that he would not be going with her as he was doomed to remain mortal for his crime.

Merlin turned up at the last minute and saved Arthur by attacking and killing both Aulfric and Sophia with Sophia's sidhe staff. Merlin kept the staff afterwards. (The Gates of Avalon) This was the staff that merlin later used to destroy Grunhilda tuning her into pixi dust 

Trivia

 * "Sophia" is greek for wisdom