The Summer Goddess

When Asta's nephew is taken by slavers, she pledges to her brother that she will find him, or die trying. Her search takes her from the fading islands of the Scattering, a nation in thrall to a powerful enemy, to the port city of Abonnae. There she finds a people dominated by a sinister cult, thirsty for blood to feed their hungry god. Haunted by the spirit of her brother, forced into an uncertain alliance with a pair of assassins, Asta faces a deadly choice—save the people of two nations, or save her brother's only son.