If you're a truly daring explorer, the great chasm through the middle of the dungeon connects all three levels, but gaining this level from the upper level (Caverns of the Mad Morlock) is usually done using the rough-hewn stairs near the top of the map. The primary inhabitants of this level have constructed a tunnel leading to the surface, which they access via the secret chamber in the bottom right corner of the map. The lower dungeon level (Fane of Hisrathi) is accessed via the staircase in the temple antechamber. The temple is the long capsule-shaped chamber in the top right corner of the map.
The Sanctum dungeon level is primarily populated by cultists, guards, and followers of the Cult of Cleansing Flames. However, Lishixa, the medusa-sorceress, and Reginald, her undead half-ogre lover (she's got creepy taste in men), inhabit the cavern areas along with a savage and drug-addicted pack of Lishixa's morlock slaves. The cultists have an uneasy truce with Lishixa.
Image download links:
Map 2, Sanctum - .png, hi-res
Map 2, Sanctum - .png, low-res
A Wee Bit of History: I used the Cult of Cleansing Flames back in the early days of 3rd edition D&D during a brief campaign set in Greyhawk. The cult is an offshoot of the elemental fire worshippers from the Temple of Elemental Evil. Led by Bayabaset the Burnt Priest (and his "lieutenants" Vasroth the Impaler and Ignia the Flame Bitch), the cultists escaped the destruction of the temple and established their own lair and temple, hidden in the northern reaches of the Lortmil Mountains. For the past few years, the cult has grown steadily, recruiting new followers and bulking its store of magic and arms. Recently, Bayabaset performed a summoning ritual that called forth the evil lord Hisrathi from the elemental plane of fire. Hisrathi is an elemental, but an evil demonic one. The cultists worship him as their true god—one who will oversee a new age once the infidels of the Flanaess are cleansed by his purifying fire!