Bastion of Broken Souls, softback adventure for D&D 3rd/3.5th edition, by Bruce R. Cordell
“The Blood of Ancient Battles Rises
An eternal demonic war draws dangerously close to an end, threatening the balance of all existence. At the crux of this chaotic feud resides a legendary terror fixated upon immortality at any cost. Only the most powerful heroes can hope to defeat a force that lies beyond the influence of the gods.
Bastion of Broken Souls is a stand-alone adventure for the DUNGEONS & DRAGONS game. Designed to challenge 18th-level D&D heroes, it pits them against some of the most powerful beings in the multiverse.”