Deep within the hives of the Calixis Sector, vile gangs wage tiny but deadly wars with Enforcers. By the flickering light of ancient lamps the streets of the underhive are home to many dangers that obfuscate the truths that Acolytes might desperately seek This book presents material for Arbitrators, Scum, and all Acolytes who operate in the arena in the Warhammer 40,000 Dark Heresy Roleplay Game, ideal for players looking to expand their characters into the depths of the underhive!