An excellent overview of his devilish plane of Gehenna by Geoffrey Dale I only found on DriveThru RPG (it's not on Dale's website at Spellbook Games). Dale authored the old Judges Guild product, "Inferno" which is at least as deadly as "Tomb of Horrors" and doesn't kill you with traps. This primer explains the infinite plane of Gehenna and how to escape PC's must travel through the Inferno (Malebolge). Our gaming group is using this to enhance our gaming through "Inferno," but the primer really is intended to flesh out the forthcoming "Inferno: Journey through Malebolge" for a complete hellish experience. The product uses Dale's own game system, "Portal to Adventure," which at first glance seemed obtuse (GTET?), but is actually pretty simple (oh, "Greater Than or Equal To"). In any event, most stats such as damage, HD, & HP are AD&D compatible and the remaining stats can be converted in a straightforward way to AD&D rules which is what our group is doing. A great malevolent setting at under a buck!