The Diamond Fortress

The Diamond Fortress is a vast structure resembling a titanic diamond embedded in the ground, pulsating with evil power and inhabited by horrid crystalline demons intent on destroying the Material Plane and transforming the world into lifeless crystal. Only the player characters can stop the masters of the fortress before they unleash their terrible crystalline army and bring doom to the land. Set near a large town famous for its frontier spirit, the Diamond Fortress is full of magic and terrible monsters. Can the player characters destroy the magic holding it to the Material Plane, or will the demonic forces contained within come forth to transform the world into lifeless crystal? A d20 adventure for 4 to 6 characters of 11th to 13th level.