The Demon Sovereign: Book 9 of I Shall Seal the Heavens

Meng Hao, having reached unparalleled power as an Immortal and the Son of the Mountains and Seas, faces a dire crisis. Chu Yuyan, the only person to whom he owes a debt, has had her soul stolen and taken to the Eighth Mountain.

Driven by a need to settle old debts, Meng Hao journeys to the Eighth Mountain and Sea, home to his mother's clan. He quickly discovers that far more than one soul is at risk. The entire Nine Mountains and Seas face an impending threat: the Thirty-Three Heavens, ancient oppressors of the realm, are descending.

No Immortal can stand against them, but perhaps a Demon Sealer who is also a Demon has a chance to protect everything he holds dear. The fate of the Nine Mountains and Seas rests on his shoulders.