Sage Alexander - Underworld Rising - Sage Alexander Series, #6

Two hundred original Angelic Response Council members traveled to the surface from the depths of Tartarus thousands of years ago. The descendants of this group, including Sage Alexander and his band of warriors, have battled Dark Beasts ever since. But when Hadley Mae, gifted with Sight, has a vision of a short battle between the Prince of Wrath and a young man bearing an ancient mark, everything Sage thought he understood about the past is turned on its head.
When Sage and his team find the mysterious stranger, they discover that he has his own agenda and it doesn't include Sage Alexander. But they need each other. Desperately. Because more than in any other time in history, the Dark Beasts are coming. The underworld is rising.