The King Beyond the Gate (Drenai Series)

Once the mighty fortress had stood strong, defended by the mightiest of all Drenai heroes, Druss, the Legend. But now a tyrannical, mad emperor had seized control of the fortress, and his twisted will was carried throughout the land by the Joinings --- abominations that were half-man, half-beast. Tenaka Khan was a half-breed himself, hated by the Drenai for his Nadir blood and despised by the Nadir for his Drenai ancestry. But he alone had a plan to destroy the emperor. The last heroes of the Drenai joined with him in a desperate gamble to bring down the emperor -- even at the cost of their own destruction.