This book serves as a foundational guide for the Ars Magica roleplaying game, focusing on the intricate world of covenant building and management. It details the essential elements required to establish and maintain a magical covenant within the Ars Magica setting, covering aspects from the recruitment of magi and companions to the development of magical traditions and the management of resources. The text provides frameworks for understanding the political, social, and magical landscape in which a covenant operates, offering guidance on navigating challenges and fostering growth.

As a supplement for the Ars Magica roleplaying game, City & Guild is designed to provide players and gamemasters with the tools to create and manage their own magical covenants. The material focuses on the intricate details of covenant life, offering structured rules and narrative prompts. Its reception within the Ars Magica community is generally positive, with players appreciating the depth of options for covenant development and the way it enhances the game's core themes of magical research and political intrigue. The book is seen as a valuable resource for those looking to deepen their engagement with the game's world-building and strategic elements.