The Riddle: The Second Book of Pellinor (Pellinor Series 2)

Maerad is a girl with a tragic past, but her powers grow stronger by the day. Now she and her mentor, Cadvan, hunted by both the Light and the Dark, must unravel the Riddle of the Treesong before their kingdom erupts in chaos. The quest leads Maerad over terrifying seas and glacial wilderness, until she is trapped in the icy realm of the seductive Winterking. There, Maerad must confront what she has suspected all along: that she is the greatest riddle of all.