From publisher blurb:
The Primal Order reigns supreme. Also known as TPO, The Primal Order is the premiere resource for using religions and deities effectively and creatively in roleplaying games. Explore how deities gain power, learn why they need worshippers and temples, discover why they provide their priests with spells, and much more. TPO also offers detailed guidelines for the creation of artifacts, suggesting strategies for their design and use.
Heralded since its initial release as one of the most innovative and useful roleplaying supplements ever published, TPO is an invaluable tool for campaign development. Get ready—your roleplaying experience is about to be transformed!
This book is not a roleplaying game; it must be used with an existing roleplaying game system, such as those listed below.
The Primal Order is what we call a "capsystem": a system of rules designed to enhance and extend any game system on the market.