Muster
The ancient game of Dungeons & Dragons is played for victory. We play to improve and learn. There is no fairness of sport nor soporific of power fantasy¸ merely the earnest exploration of the possible and the fantastic.
Muster is a friendly introduction to the particular ethos and technique of playing D&D as a wargame¸ a kriegsspiel. It's for both players and referees interested in learning about this distinct approach to the game. For best results¸ study Muster alongside the old school D&D rules text of your choice.
The book is free and free to share¸ CC-licensed. Hopefully it'll be useful for both new and advanced gamers in thinking about the hobby!