A Ptolus adventure for 11th level characters.
Originally released in 2002 as a 3.0 edition adventure module. As this was before Ptolus was released there is no mention of Ptolus itself in the module. It did come from Monte's Ptolus campaign and all the maps and locations from the module can be found in the latter released campaign setting.
The book was updated to 3.5 edition and re-released with the Ptolus logo after the release of the campaign setting in 2006.
From the publishers website:
Deep below the surface, in the sunless lands of the Netherdeep, creatures of darkness build weapons and amass armies, dreaming of invasion. An attack on a peaceful elven shrine in Emerald Hill sends the heroes on a quest to retrieve stolen artifacts and kidnapped friends. All signs point to the actions of the dark elves of Ul-Drakkan, far below the city of Ptolus. However, even within that ancient fortress, there exists a deeper darkness.... Underground enemies lurk beyond every twisting passage, and strange creatures abound. The foul culture of the dark elves is both decadent and cruel, and the heroes may discover that they've stumbled into a web of deceit and treachery that threatens the lives of all who oppose the dark elf Queen. Can the heroes complete their mission without being discovered, or have their very actions been orchestrated by the Queen of Lies?