The Sorcerer's Equal: the Telepath and the Sorcerer Book 3. Jaclyn Dolamore

Following a fierce battle, Grau's life hangs in the balance. Velsa seeks healing and refuge in the land of Laionesse, only to learn that Grau's injuries may be beyond help--unless Velsa and her friends can beg a favor from the great necromancer Dormongara, who lives alone in a castle on a mountain and is notoriously unkind to visitors. Indeed, the steep price he demands will have unexpected consequences, bringing an old nemesis back into Velsa's life along with a notorious gang of bandits. Velsa and Grau must consider how many times they will run from their fate and what tests true love can withstand in this conclusion to The Telepath and the Sorcerer trilogy.