Set 3: Companion Rules Expansion rules for the D&D Basic and Expert Sets. This is set #3. To be able to play the companion set, you should already have played both, D&D Basic Set and D&D Expert Set. Players Companion - Featuring rules for unarmed combat, strongholds, and new weapons and armor. Plus more advanced rules and spells for your characters. Dungeon Masters Companion - New rules for ruling realms and the clash of kingdoms. New treasures and monsters. Plus new adventures for your high-level characters.