From the introduction: A mysterious portal has appeared in an inhabited area. Its arrival has eradicated a large village. The local government is looking for adventurers to investigate. A huge mound of earth sits where a large village once stood. A strange black portal stands quiet ominously flanked by two huge stone reliefs of incredible horror. The portal emanates an aura of elemental and planar magic. Swallowing anyone that enters, the exit disappears; there is no light source. Inside is a long corridor. The floors are smooth polished stone the walls rough and jagged pocked by hundreds of small tunnels.