Demon Ascendant: Lord of the Forsaken

Kaelen Veyr, a kindhearted healer summoned to Aetherion, is betrayed by his Hero Party on the 50th floor of the Labyrinth of Eternity and left to die. He accepts the power of the ancient demon Azrath, becoming the Abyssal Sovereign, then conquers the remaining labyrinth floors and rises as a godslaying force. After rescuing Nyra, an enslaved cat demi-human, Kaelen abandons indiscriminate destruction and builds a kingdom where persecuted races can live freely. With Nyra, the dragon warrior Ryshara, and the elven princess Elowen at his side, he challenges the oppressive Human Empire while the ancient Demon King Malachar awakens. To save his new homeland, Kaelen must eventually fight beside the companions who betrayed him.