Redoubt (Collegium Chronicles Series #4)

Mags, a young Herald trainee in Haven, the capital city of the kingdom of Valdemar, has talents not commonly found in Herald trainees. Recognizing this, the King's Own Herald decides to train Mags as a spy in order to uncover the secrets of a mysterious new enemy who has taken an interest in Mags himself. Why is the even deeper mystery. The answers can only be found in the most unexpected corners of Mags' past...assuming he can live long enough to find them.