HackJammer is HackMaster's parody of the Advanced Dungeons & Dragons setting, Spelljammer. Specifically, it uses material from Spelljammer: AD&D Adventures in Space by Jeff Grubb, Lost Ships by Ed Greenwood, The Complete Spacefarer's Handbook by Curtis Scott, War Captain's Companion by Dale "Slade" Henson, and the Monstrous Compendium Appendix. From the back cover: Take your HackMaster campaign to the stars with this new reference work. Includes all the rules you need to run a spacefaring campaign along with valuable details on Aldrazar's (Garweeze Wurld's) solar system and nearby star systems. Also included are: - 8 new character races - 18 new spells - 45 new monsters - New quirks, flaws, and skills - Many new and unique magic items