A Guide to Thieves' Guilds (d20)
This book provides an abstract system for running thieves' guilds in any OSR-style game. While written for Old School Essentials¸ the system contained is easily adapted to other rulesets. It provides guidelines for establishing and recruiting for a guild¸ generating revenue¸ and resolving conflicts with rival Guilds¸ with a focus on higher-level play for thief and assassin characters.