The Oath of Stonekeep — Troy Denning

There were dark things in the valley...a host of throgs and shargas and hell-forged creatures sweeping out of the frozen wilderness to murder and ravage and take what men were too weak to defend...

STONEKEEP
An ancient citadel blessed by the gods with peace, freedom--and safety from the dark ones. Five hundred years ago, the hero Drake raised the walls of Stonekeep on the unholy grave of Khull-khuum, the Shadowking. Now, the good people of Stonekeep can barely remember such legends. They have forgotten the power of evil--and are as happy, and vulnerable, as sheep...

But darkness again threatens the land. Ulger the Cruel has returned from exile, and he plans to release Khull-khuum from his tomb. Stonekeep will need a new hero...

Cassius of Kural is the only human who understands the danger. His ally, Pendaran, is the only sorcerer who will help him. Together, they must wage a war against darkness with a makeshift army raised from the realms of dragon and faerie--an army they can barely control...