user summary: B/X Companion is a companion volume to the 1980 edtion of Basic and Expert D&D edited by Tom Moldvay. The companion level book for the Moldvay edition of Basic D&D was never released. The newer Mentzer edition of D&D replaced the Moldvay edition and companion level materials were specifically added to that edition via the Companion set and the Rules Cyclopedia. Here is a bullet-point list of the material added for Moldvay D&D by the B/X Companion: Character levels 15-36 70+ new monsters designed for high level play. 100+ new magic items plus an entirely new (not present in Basic D&D) class of magical items. Spell tables up to level 7 for clerics and level 9 for magic-users. 58 new spells. Additional abilities for high level characters. The B/X Companion also provides rules for running Dominions, commanding armies and engaging in mass combat, and adventuring in hazardous environments and other planes.