Red Fire by Deidre Knight

Eternity has become a prison for Ajax Petrakos. Centuries after he and his Spartan brothers made their bargain for immortality, Ajax struggles to maintain his warrior’s discipline. His only source of strength is his hope that he will soon meet the woman once foretold to him—the other half of his soul, Shay Angel.

Ajax searches for his destined mate on the haunted streets of modern-day Savannah, but he isn’t the first to find her. Shay, the youngest of a powerful demon-hunting clan, can see the monsters that stalk the steamy Southern night—an ability that draws the deadly attention of Ajax’s worst enemy.

As she and Ajax race to solve a chilling prophecy—one that could spell Ajax’s death if they don’t succeed—a fated passion arises, threatening to sweep away everything in its path.