From publisher blurb:
Welcome to the world of Shadows over Vathak, a realm where the abominations known as the Old Ones seek to destroy humanity. It is a world of darkness and despair, where even the light of the One True God is often corrupted and twisted to serve sinister ends. As players, you may be heroes representing a bright point of light in the encroaching shadows of evil or you might just be survivors, living day by day however you can, survival your only goal. In Vathak, even joy is mingled with the bitter ashes of despair and hopelessness.
What you have here is additional GM information to augment the material presented in the Shadows over Vathak Campaign Guide. New locations, monsters, and more are detailed in the pages of this book, tied to one of the specific regions of Vathak. Even if your campaign does not take place in this region of Vathak, that does you cannot use the material in this book. While the material here in is based on a specific region, it is also designed to fit the overall themes of Shadow over Vathak as a whole. As the GM, you should modify the material in this book as you see fit to create the story that you want to tell. Additionally, the material presented in this book can be ported over to whatever campaign world you are using.