Throne of Glass #6: Tower of Dawn book by Sarah J. Maas

Chaol Westfall and Nesryn Faliq have arrived in the shining city of Antica to forge an alliance with the Khagan of the Southern Continent, whose vast armies are Erilea's last hope. But they have also come to Antica for another purpose: to seek healing at the famed Torre Cesme for the wounds Chaol received in Rifthold.

After enduring unspeakable horrors as a child, Yrene Towers has no desire to help the young lord from Adarlan, let alone heal him. Yet she has sworn an oath to assist those in need—and will honor it. But Lord Westfall carries shadows from his own past, and Yrene soon comes to realize they could engulf them both.

In this sweeping parallel novel to the New York Times bestselling Empire of Storms, Chaol, Nesryn, and Yrene will have to draw on every scrap of their resilience if they wish to save their friends. But while they become entangled in the political webs of the khaganate, deep in the shadows of mighty mountains where warriors soar on legendary ruks, long-awaited answers slumber. Answers that might offer their world a chance at survival—or doom them all . . .