The Shattered Gates of Slaughtergarde (3.5e)
Centuries ago¸ forces of good and evil collided in a titanic battle at the mountain fortress of Slaughtergarde. Armies of men¸ angels¸ elves¸ and dwarves fought and defeated a rampaging demon horde¸ banished its demon prince¸ and tore Slaughtergarde apart¸ hurling it back into the Abyss. However¸ the destruction of Slaughtergarde was incomplete. Parts of the fortress were embedded underneath the Valley of Obelisks¸ buried for all time. Now¸ malign forces have found Slaughtergarde's dark chambers¸ and they toil ceaselessly to restore the magic gates that will reconnect Slaughtergarde to the Abyss. If they aren't stopped¸ a new demon horde may emerge from the shattered fortress to rampage across the world.