Tower of Dawn by Sarah Maas (Throne of Glass #6)
Chaol Westfall has always defined himself by his unwavering loyalty, his strength, and his position as the captain of the Guard. But all of that has changed since the glass castle shattered, since his men were slaughtered, since the king of Adarlan spared him from a killing blow, but left his body broken. His only shot at recovery lies with the legendary healers of the Torre Cesme in Antica. And with war looming over Dorian and Aelin back home, their survival might lie with Chaol and Nesryn convincing its rulers to ally with them.