Disquiet Gods (Sun Eater Series #6) by Christopher Ruocchio

The sixth novel of the galaxy-spanning Sun Eater series merges the best of space opera and epic fantasy, as Hadrian Marlowe continues down a path that can only end in fire.

The end is nigh.

It has been nearly two hundred years since Hadrian Marlowe assaulted the person of the Emperor and walked away from war. From his Empire. His duty. From the will and service of the eldritch being known only as the Quiet. The galaxy lies in the grip of a terrible plague, and worse, the Cielcin have overrun the realms of men.

A messenger has come to Jadd, bearing a summons from the Sollan Emperor for the one-time hero. A summons, a pardon, and a plea. HAPSIS, the Emperor’s secret first-contact intelligence organization, has located one of the dreadful Watchers, the immense, powerful beings worshipped by the Pale Cielcin.

Called out of retirement and exile, the old hero—accompanied by his daughter, Cassandra—must race across the galaxy and against time to accomplish one last, impossible task:

To kill a god.