Darker by Four

As an Exorcist-in-training, Rui is tasked with purging the city of Revenants, souls of the dead who have returned to feast on the energy of the living. For Rui, the fight is personal - a Revenant murdered her mother, and she wants revenge. But Rui's first encounter with a Revenant is nothing like she expects. And when she is nearly killed protecting Yiran, the spoiled, magicless youngest son of one of the most powerful families in the Exorcist Guild, Rui uses a volatile spell to transfer her magic to him.

When an accident causes Rui’s power to transfer to Yiran, everything turns upside down. Without her magic, Rui has no tool for vengeance. With it, Yiran finally feels like he belongs. That is, until Rui discovers she might hold the key to the missing death god and strikes a dangerous bargain with another King.

The world has moved on. With the missing death god restored to the underworld, it appears that equilibrium has been regained. But the Nothing continues to threaten the underworld—and the mortal realm. Trapped in Hell, Zizi fights the takeover of his soul by Four's. As he begins to access Four's memories, he discovers a tragic love story that could be the key to keeping the mortal realm safe. Now, Zizi must defy his fate and escape Hell once more.

Rui has her life back together—or so it seems. Hailed as a hero, she’s finally on her way to becoming an important member of the Exorcist Guild. But she knows the Hybrid Revenants are still out there, and they’re planning something big. Something evil. Zizi is trapped in the underworld. As his mortal body deteriorates, he realizes he can access the Fourth King’s memories, which may be the key to keeping the mortal realm safe. To save the girl he loves, he must defy fate—and escape Hell.