S&S (d20) - RAPPAN ATHUK 2 - THE DUNGEON OF GRAVES: THE MIDDLE LEVELS (2000)

From the back cover:

Deeper into the Dungeon!: Though you lost several of your companions in the Upper Levels, you want more! Do you dare assault the hidden Temple of Orcus? Can you locate the famed Passage to the Gates of Hell? Will you find the Titan Ereg Tal? Or will you fall prey to the Phase Minotaurs or Kazleth the Minotaur King? You must descend still further into Rappan Athuk to learn the answer. A pity you wont live to tell the tale.

Descend into Evil: Rappan Athuk The Middle Levels continues the adventure into the most famous and feared dungeon in all the lands. Designed for characters of 6th to 9th level and higher, The Dungeon of Graves challenges even veteran adventurers. This book is the second in our three-part R series of modules, which detail all 26 levels of this notorious dungeon.