Sirens of the Blood Sea

From publisher blurb:

As if the polluted waters of the Blood Sea weren't terrifying enough, within these covers you will find a deep dive into a new native creature dragged up from its depths: the Siren. With the power to enrage or enchant its humanoid victims, this beautiful parasite should worm its way into your players' nightmares.

In this book you will find:

Lore including the siren's lifecycle, origins, and social structure
Game statistics for three siren variants
A mini-adventure showcasing them
A playable race, in case you’ve been waiting for the chance to play a character with an implanted titanspawn symbiote