Book one in the Tales of the Penitent trilogy
Long ago, the youngest of the gods fell into the clutches of an ambitious mortal, a usurper who took what he wanted and almost destroyed the world. The Elderkin, the old gods, imprisoned the mortal in the heart of a mountain and took away the young god's beauty, name, and tears. Then they fled the earth, leaving man godless. But they left a prophecy behind that if the Nameless God's birthright is returned to him before the mortal breaks free, then the Elderkin will return.
Now the burden of this prophecy rests on the shoulders of a reluctant boy. As a Scribe for the Guardians, the group of men and women dedicated to returning the gods and keeping the mortal imprisoned, Sam has been mistreated, ordered about, and mind-scrambled. Now he has to fulfill the prophecy? Not likely—the boy would much rather damn it than do it. But it doesn't seem like he's going to have much choice in the matter.