Onyx Storm by Rebecca Yarros

In Onyx Storm by Rebecca Yarros, Violet must seek allies beyond the Aretian wards after peace talks with the revolutionists falter and a threat closes in. Her mission is to find the mythical seventh dragon breed—the irids—believing they are the key to defeating the venin army and finding a cure for Xaden, who has begun to turn venin. While this quest is central, Violet must also navigate an increasingly dangerous environment, trust those around her, and keep a huge secret that could destroy everything.