Demon's Gate

Valdar, heir to the throne of Dhulon, was in the fabled imperial city of Schaerisa to pay his respects to the somewhat enigmatic new emperor. But then he ran into his old mentor, the sorcerer Nyrthim - who was supposed to be dead. He learned that Nyrthim's death had been faked so that the sorcerer could be free to investigate tales that demons, once banished, were returning to the world. And unfortunately, the tales understated the danger.
Once, demons ranging from deadly imps to evil demigods had ruled the world. They had been cast out and confined to the nether world only with powerful sorcery, using spells long lost. Now someone is trying to summon the most powerful - and unspeakably dangerous - of these accursed creatures back to the world of men, hoping to conquer it through them. Unless Valdar and his companions at arms can thwart the plan, creatures evil beyond all human conception will return to rule the world.
And this time, nothing will drive them back into the outer darkness. Darkness will rule - forever.