Master of Restless Shadows #2 by Ginn Hale

As a schoolboy, Fedeles Quemanor barely survived being possessed by sorcery. Now he’d gladly abandon all matters of magic to more ambitious people. His happiness lies in more simple things: riding horses, the joy of friends and family and dancing with Ariz Plunado.
But when he discovers that Hierro Fueres, the Duke of Gavado, is raising an army of enthralled assassins to seize the crown, Fedeles is shaken to the core. Worse is the revelation that the ancient spells protecting their nation from an ravenous curse are being dismantled.
The murderous power lurking in Fedeles’s shadow could be enough to secure the nation of Cadeleon. If only Fedeles can face the darkness that once possessed him.
But even as Fedeles takes on the challenge, his agents, Atreau and Narsi, learn that the threat at heart of the capitol has grown beyond the bounds of their nation. Unless they take action, Count Radulf, the ferocious Scarlet Wolf of Labara, will destroy it and all of Cadeleon along with it.