Summary: A magical pool offers knowledge, but those who might abuse it put themselves at risk.
Sights and Sounds: It is dark here. A DC 20 Listen check (DC 20 Perception check for Pathfinder) reveals a faint scratching sound that comes from both 3D and 3E (the ghouls).
You see a massive chamber filled with cobwebs and dust. A shallow pool twenty feet across lies in the middle of the room, with tall pillars to the east of it, each carved to look like a tall, beautiful, human woman. The ceiling is vaulted, and a crescent moon has been painted at the highest point, which is directly above the pool. Although the paint is chipped, it still retains a peculiar luster that reflects light with a glistening glow. The walls sport a few empty sconces, and you see an imposing set of bronze doors on the east wall. These double doors bear images of winged horses rearing majestically.
Secret Door: The secret door that gives access to the passage leading to area 5 is not too difficult to find (DC 18). An empty sconce on the wall serves as a lever that causes the door to pivot easily and quietly.
Moon and Pillars: Anyone making a DC 15 Knowledge (religion) check recognizes the moon symbol on the ceiling and the images in the pillars as that of Glarias, Goddess of the Moon. Hers is a minor and mostly dead cult focused on secret lore and divination.
The Pool: The pool has a raised stone lip around its edge. The water is about a foot deep, appears surprisingly pure and clear, and has a faint magical aura (divination). If anyone speaks the magical, sacred phrases found in the book in 3A, the water rises up from the pool in the shape of a beautiful maiden. This watery creature is a minor manifestation of Glarias herself. The PC who spoke the phrases can ask the maiden a single yes or no question as described in the spell commune (commune, for Pathfinder). She will answer to the best of her ability, but the GM should be careful about adjudicating the answers. Glarias is currently imprisoned (in deepest bowels of this very dungeon), and her knowledge about current events in the world at large may be limited. Her divine knowledge of the dungeon, however, is extensive.
The pool can be used safely once. If the same person attempts a second question without waiting until asking again in the same phase of the moon (which is to say, in one month's time), or if another person attempts to ask a question in the same month as another character, they get an answer, but the door to area 3D opens and the ghoul comes out to attack. If someone attempts it again, he or she gets an answer, but the door to area 3E opens and the ghast comes to attack. After that, further attempts are impossible for one month.
Both Chasmal the werewolf in area 37 and the doppelgangers on Level 2 occasionally use this pool, although they haven't in over a month, so the first question the PCs ask is safe. Later attempts on subsequent visits may not be if Chasmal or the doppelgangers are still around.
3A. The bronze doors leading into this room are locked, but the lock is more for show than anything (DC 14 Open Lock, DC 14 Disable Device for Pathfinder), and the key can be found in 3C. Beyond the doors is an old library, although much of it lies in ruin, with broken shelves and rotten books. A DC 15 Search check (DC 15 Perception check for Pathfinder) produces 1d6 intact books on various (mundane) topics, each worth 1d6 gp. This check can be performed up to five times, with new books found each time. One of the first books found will be Glarias' Pool. This book isn't like the others. Anyone studying it for at least an hour learns the proper magical phrases which can be spoken next to the pool to allow one to ask the pool a question. The book cautions that punishment will come to those who abuse the power of the pool.
3B. Aside from some old, rotten furnishings, this room is empty. The door to area 20 is bluesteel and cannot be opened without the password "Desitam." This word can be learned in area 19 or from Chasmal the werewolf in area 37.
3C. This chamber is filled with wrecked wooden furniture, mostly chairs, tables, and bookshelves, old and rotten. A few rotted and useless books lie amid the wreckage, but nothing of value other than a large, ornate bronze key that unlocks the doors leading into 3A. The key itself is worth 15 gp.
3D. The door to this chamber is locked (DC 25 to open), but opens when the pool is consulted twice in one month. Inside waits a creature called a chastisement ghoul, appearing exactly as a normal ghoul but with a half-moon symbol painted prominently on its forehead. The ghoul has been created through Glarias' power, and as such it will not attack a worshipper of Glarias. However, all Glarias's followers within 20 feet of the ghoul are magically chastised by its censure stare. This chastisement acts exactly as a bestow curse (bestow curse for Pathfinder) spell (no saving throw) that lasts until they go to Glarias' temple and seek atonement in a prayer that lasts an entire night. Sadly, the temple is now devoted to the Beast God (see area 6). While the PCs can still gain atonement there, they then fall under the effects of a powerful geas (geas, for Pathfinder and again, no save) to free Glarias from her imprisonment deep in the dungeon. The characters gain no special knowledge of how this can be done, but they don't suffer penalties or drawbacks for not doing it immediately, either. They just have to do it at some point. (This should be treated more as a roleplaying opportunity than a game mechanic issue.)
The ghoul attacks non-worshippers of Glarias, focusing its attentions on the offending user of the pool.
There's nothing else in this room. If the ghoul is destroyed, a month later a new ghoul is summoned and the door closes and re-locks, set to punish those misusing the pool once again.
3E. This chamber is identical to 3D, except instead of a ghoul it houses a chastisement ghast, complete with the moon symbol on its forehead. It has the same censure stare and restrictions as the ghoul. The room produces a new ghast after a month as described in 3D.