Ashes of Man: The Sun Eater (Book Five) by Christopher Ruocchio

In "Ashes of Man," the fifth installment of Christopher Ruocchio's Sun Eater series, the galaxy is engulfed in conflict. The Cielcin, an alien race united under their Prophet-King, wage war against the Sollan Empire following the betrayal of the Commonwealth. Amidst this turmoil, rumors circulate that Hadrian Marlowe, the protagonist, has perished. However, he survives with the aid of Valka, a witch, and together they uncover a chilling reality: the deities worshipped by the Cielcin are real and seek to plunge the universe into darkness. As the Cielcin forces close in, threatening humanity's existence, Hadrian and Valka must navigate political intrigue and personal struggles to confront this existential threat.