ComStar has controlled the Inner Sphere's interstellar communications and other technology for centuries. ComStar single-handedly stopped the Clan invasion, then failed in its attempt to take control of the Inner Sphere. Now the organization responsible for keeping the Inner Sphere together has split in two factions.The ComStar Sourcebook recounts the organization's history, describes the technology it preserved, and reveals the circumstances that broke it apart. The ComStar Sourcebook also describes the new ComStar order and the splinter organization Word of Blake. It includes new BattleMechs from both groups, and an 8-page color section featuring ComStar and Word of Blake uniforms, insignia, and equipment.