XDM: X-treme Dungeon Mastery is a role-playing game book by American writers Tracy Hickman and and illustrated by Howard Tayler. Purporting to be the work of a 'secret society' of extreme game players, the book both casts a satirical eye on role-playing games and offers practical application advice on improving the design and play of role-playing games. It includes its own complete role-playing game system as well.