Power Through Decadence is the first organization source book for Enter The Shadowside. It covers one of its more mysterious factions, the Greater Thelema Society: an elite club of world-wide power-brokers who master occult forces in an endless Game of Pawns.

The source book includes information on GTS's history, organization, Skills (and Skill Progression), advice for creating an archetypical character, and GTS's relationships with every other Shadowside organization. Character stories have been artfully weaved in between chapters to cement the information and provide flavor and tone to the material.

This book is a supplement to Enter The Shadowside - Core Book.