Darklands (The Rhenwars Saga, #2)

Compelled to obey the dark god he pledged his soul to, Darien finds himself tasked with delivering the people of the Black Lands from under the curse of darkness which shrouds the skies. With the enemy mage Azár, Darien sets out across a barren darkscape to assume his place as the leader of a people who despise him.
As he journeys deeper into the shadowed waste, Darien is confronted with difficult truths that force him to question every loyalty he has ever held. For there, in the brutal proving grounds of the north, Darien will be inexorably forged into the most dangerous adversary the Rhen has ever faced.