Ptolus: The Spire (3.5e)
Soaring above the characters' heads at all times¸ the Spire is both awe-inspiring and daunting. Although often obscured by clouds¸ it poses an everpresent threat and a reminder of the region's dark history.
"In this book you will find details about Goth Gulgamel¸ the fortress of Ghul: the Skull-King and Half God. It is a place of great evil and great power¸ of interest to high-level characters as a site to explore.
"You will also find a chapter describing Jabel Shammar¸ almost certainly the worst place in the world. Jabel Shammar is the fortress at the top of the Spire¸ built by the Dread One himself. You get a room-by-room description of the stronghold plus ideas for staging an exciting campaign climax there.