Destroy the Day by Brigid Kemmerer

In the thrilling conclusion to the Defy the Night series, New York Times bestselling author Brigid Kemmerer crafts heartrending twists and devastating turns that will keep readers breathless to the very end.
Left for dead, but desperate to survive . . . they have one last chance to save their kingdom.

Prince Corrick is out of options. Held captive by the vicious Oren Crane, he's desperate to reunite with Tessa, but will need to ally with the rebel leader Lochlan, who until now wished him dead. An unlikely but deadly pair, Corrick and Lochlan must plot their next moves carefully. . .
An island away, Tessa Cade is heartbroken and angry. Grieving Corrick, and unsure how to find a way back to Kandala, she doesn't know who to trust. Until Rian-the man she trusts least-makes an offer: aid in a plot to finally oust Oren Crane and see what the future holds. . .
Meanwhile in Kandala, Harristan is dethroned and on the run. He's struggling to unite the rebels in his fractured kingdom, but he finds support-and maybe more-in unexpected places.
Can Harristan be the king his people need? Can Corrick and Tessa find their way back to each other? As outside threats loom and the fires of revolution burn from within, time is running out to save their kingdom.