Das Buch des Spielleiters (The Game Master's Book) contains additional rules and game master information for the Osiris Rollenspiel. "Das Spielerhandbuch" is also required to play.
- A more detailed look at dice mechanics,
- Character advancement
- Information on injuries, diseases, poisons, phobias, madness, and healing
- World and adventure creation advice
- Advanced combat rules
- Game master advice