"Tome of Battle" introduces a new combat subsystem for the D&D game. "Tome of Battle" introduces new rules for players who want new and interesting combat options for their characters. The nine martial disciplines presented within allow a character with the proper knowledge and focus to perform special combat maneuvers and nearly magical effects. Three new martial adept base classes are presented that allow a character to develop their discipline even further. Also included are new feats and prestige classes that build on the disciplines, new magic items and spells, and new monster and organizations.