KING OF SCARS - Leigh Bardugo

The boy king. The war hero. The prince with a demon curled inside his heart. Nikolai Lanstov has always had a gift for the impossible. Yet with each day, a dark magic within him grows stronger, threatening to destroy all he has built. His country in Nikolai's first love, and whatever in demands, he will give.  Zoya Nazylensky has dovoted her life to honing her deadly talents and rebuilding the Grisha army. Despite their magical gifts, Zoya knows the Grisha cannot survive without Rakva- and Rakva cannot survive a weakened king. Zoya will stop at nothing to help Nikolai secure the throne, but ahe also has new enemies to conquer in the battle to come.  Far north, Nina Zenik wage her own kind of war against th epeople who would see the Grisha wiped from the earth forever. Burdened by grief and a terrifying power, Nina must face the pain of her past if she has any hope of defeating the dangers that await her on the ice.