The Seat of Magic — J. Kathleen Cheney

Magical beings have been banned from the Golden City for decades, though many live there in secret. Now humans and nonhumans alike are in danger as evil stalks the streets, growing more powerful with every kill....

It's been two weeks since Oriana Paredes was banished from the Golden City. Police consultant Duilio Ferreira, who himself has a talent he must keep secret, can't escape the feeling that, though she's supposedly returned home to her people, Oriana is in danger.

Adding to Duilio's concerns is a string of recent murders in the city. Three victims have already been found, each without a mark upon her body. When a selkie under his brother's protection goes missing, Duilio fears the killer is also targeting nonhuman prey.

To protect Oriana and uncover the truth, Duilio will have to risk revealing his own identity, put his trust in some unlikely allies, and consult a rare and malevolent text known as The Seat of Magic....