The Master of the Underworld is the nemesis of the pulp heroes, the antithesis of all this is decent, good, and just. No mere mob chieftain, the Master of the Underworld is a criminal genius, a master plotter whose abilities, resources, and skills make him the equal of the era's various mystery men, the champions of law that ordinary criminals fear. Just like those worthies, the Master of the Underworld's real identity is hidden from the world, unknown even to his closest cohorts. His masked visage serves both to protect his precious secrets and to frighten those foolish enough to take sides against him. And just as the mystery men employ unusual, even extraordinary equipment and tactics, so does the Master of the Underworld have his own fantastic accoutrements-weapons created by weird science, horrible devices for which the pulp world is not yet ready. This 8 page PDF is just the sort of thing needed for GMs to add depth to any great d20 Pulp campaign world, including Haven: City of Bronze.