From publisher blurb:
The Halls of Lidless Shabbath is an OSRIC(tm) module designed for 4-6 adventurers of levels 12-15.
Rolled into a yard-tall, ivory scroll tube, the worn charcoal rubbing of a giant map etched into an ancient monolith hints that travel between worlds was once easy. More enticingly, the map pinpoints the entrance to the eldritch pathway. The crude rubbing shows nothing but the location of the ancient and legendary dungeon known as the Halls of Lidless Shabbath!
The Halls are the home of the evil sorceress Shabbath. She was famed for having researched many new spells and created many unique magic items, as well as possessing fantastic treasures of gold and jewels, and the caves are also suspected to be a nexus of the planes. Little about the contents of the Halls themselves is known, save that Shabbath is rumored still to be alive, the Halls are reputedly haunted by demons, and a large warband or small army of trolls has been seen thereabouts.