The Beauty of Darkness By Mary E. Pearson

Lia has survived Venda—but so has a great evil bent on the destruction of Morrighan. And only Lia can stop it.

With war on the horizon, Lia has no choice but to assume her role as First Daughter, as soldier—as leader. While she struggles to reach Morrighan and warn them, she finds herself at cross-purposes with Rafe and suspicious of Kaden, who has hunted her down.

In this conclusion to the Remnant Chronicles trilogy, traitors must be rooted out, sacrifices must be made, and impossible odds must be overcome as the future of every kingdom hangs in the balance.