A Sliver of Redemption (Half-orcs, Band 5)

The war god Thulos marches across the world of Dezrel, recruiting soldiers into his demon army and annihilating all who stand against him. With the aid of three Kings, Harruq Tun and his friends must save the nation of Mordan, whose priest-king has sworn to the dark god, and will summon whatever nightmarish creatures necessary to maintain rule. Once freed, they can turn their attention east, to the war god's approach. Before the walls of Mordeina, and high above in the golden city of Avlimar, the last survivors make their stand against a world of death and conquest.
A SLIVER OF REDEMPTION by David Dalglish
The final battle has come.