This forum is to be used for all discussions pertaining to The Elder Scrolls IV: Oblivion, its Knights of the Nine and Shivering Isles expansions, and any user-created or premium modules.
Although you hear about other sanctuaries in books & conversation, there aren't any you can visit in the stock game. The "Vile Lair" plug-in from Bethesda has some neat stuff for assassin types, and I believe there are a number of third-party mods with DB expansions.