The Ghost King's Little Exorcist Wife

Any Good Supernatural Novels with a Powerful, Cold, and Unsentimental Heroine?

Something genuinely scary. There can be a male lead, but the main plot should focus on the mystery and its logic. The female lead shouldn't be a bleeding heart; she should be rather aloof and very capable.

The Male Lead Is a Snake, Fox, Underworld Lord, Ghost King, Mountain God, or River God, While the Female Lead Is Human

Quick Transmigration, Including a Plot Where the Male Lead Is a Ghost and the Female Lead Is Human

The story goes like this: The eldest princess of this dynasty had the male lead killed, and he became a ghost. The female lead came with a mission. The original owner of the female lead's body liked her cousin, a Deputy Minister of the Court of Judicial Review.