I made the mistake of saying "Coming soon: Level Three" in my Under the Pyramid: A Megadungeon -- Level Two post on November 7th. Here it is -- or at least the first half of it. Better late than never, I guess.
The third level under the pyramid is a group of five major areas only loosely connected together. Many characters only discovered the major area with the serpent men and never found the other areas in the rush to get to deeper levels. This was a shame because most of the really good treasure was in the other areas -- and one of those areas could provide a strong ally against the serpent men. I'll describe the this level by areas.
The Serpent People area is over half the level area-wise. There is a large cavern with a village of serpent people (and a temple to Set at one end). Over 300 serpent people (men with a serpent for a head like in the Conan stories I stole the idea from.) live in the village. All have a poisonous bite (save vs poison or paralyzed for 1d6 hours), can use minor illusions (change self type), and appear to be invulnerable (they take damage normally but look like they are never wounded until they fall over dead and the illusion fades). Most fight as 1st level fighters and favor wicked looking swords (that do 1d6+2 damage but shatter if a six is rolled). However, there are 30 "sergeants" who are second level fighters and 10 warleaders who are third level fighters. The two under-chiefs are 4th level fighters (their wives are 4th level clerics of Set who can use magic-users spells as well as clerical spells) while the chief is a 6th level fighter with two wives. They are human sisters and are the real powers behind the throne. One is a 6th level magic-user, the other is a sixth level cleric of Set. The chief and underchiefs (and their wives) have magic items, nothing super (plus +1 weapons, minor magic wands, etc.)
There are a number of rooms and chambers off of the cavern, including a prison and torture area, a "gatehouse" area where the sloping passage from level one terminates, a magic lab for the magic-using wives, a treasure vault guarded by a minor demon, a snake hatchery, and a small arena for combats.
There are no immediately obvious connections to other levels except the sloping passage from level one, a staircase going up to level two (also in the gatehouse area) and a staircase going down to level 4 in a room behind the large statue of Set in the temple. There are, however, hidden ways to other parts of the level. All but one are known to the Serpent people and are guarded either with warriors or traps.
Believe it or not, the Serpent People will be happy to let people who are not enemies (that is, are not known to have attacked and killed serpent people without cause) pass through their area for a nice donation. They make a good profit selling passage to level four for a 10gp per head donation to Set. Coming back usually costs 30gp per head, but if the returning party is badly damaged they may just try to kill them and take their stuff, depending on reaction rolls/prior history. Note that if a group fights their way out of this and returns, they will pretend like nothing happened and sell them passage again.
The Serpent people are meant to be too powerful for lower level parties to be able to wipe out. Stupid players will attack them, smarter players will treat them as a "passage tax" and wait until they are much more powerful to try to get rid of them.
Next Pyramid Post: The rest of level three.