Shadowfell

Fifteen-year-old Neryn is alone in the land of Alban, where the oppressive king has ordered anyone with magical strengths captured, but when she sets out for Shadowfell, a training ground for a rebel group, she meets a mysterious soldier and the Good Folk, who tell her that she, alone, can save Alban.

"In the final book of the Shadowfell trilogy, Neryn, the rebels, and the Good Folk must work together to survive their final confrontation with King Keldec"-- Provided by publisher.