The Forging of the Shadows (Lightbringer Trilogy #1)

It is a time of great darkness, when the sun is in danger of being forever extinguished, and mankind has been divided into two warring factions: the worshipers of the God of Light and the servants of Eternal Night. Now three unsuspecting travelers are called by prophecy to face a legion of the undead and the powers of the Dark Lord in the faint hope of reclaiming the world for the light.