This book is invaluable to understanding the Arisen and the various guilds that they can belong to. From the core rulebook you begin to get a vague and general idea about the guilds and while this works at first they can seem rather flat and boring, this book takes all of that and corrects it, adding a lot of interesting information about the guild and the roles that they play. I honestly think that if you have any intention of running mummy that you need this book.