Nightglass

In the grim nation of Nidal, carefully chosen children are trained to practice dark magic, summoning forth creatures of horror and shadow for the greater glory of the Midnight Lord. Isiem is one such student, a promising young shadowcaller whose budding powers are the envy of his peers. Upon coming of age, he's dispatched on a diplomatic mission to the mountains of Devil's Perch, where he's meant to assist the armies of devil-worshiping Cheliax in clearing out a tribe of monstrous winged humanoids. Yet as the body count rises and Isiem comes face to face with the people he's exterminating, lines begin to blur, and the shadowcaller must ask himself who the real monsters are...