I ran a large party through there once. We had the party that originated in the Dalelands and they eventually went into Kara-Tur and met some more PCs (we added some new players, and wanted to incorporate some Oriental flavor).
So the party consisted of:
Ranger (half-elven)
Barbarian (human)
Wizard (human)
Cleric (human)
Fighter/thief (dwarf)
Sohei (human)
Samurai/ninja (human)
Ninja (human)
I believe that was the entire party. They averaged in their low teen levels (13th -14th roughly).
Like Jared, we also had a powerful demon appearing in the upper levels, but in this case the demon did not chase the party out. He became an ongoing, mortal enemy. He managed to kill a few of the party members and polymorph the ninja into a mouse, which we never did end up restoring. Just didn't make the rolls!
Halaster actually appeared to the group to taunt them, and boy did the players soil their drawers when they realized it was Halaster!
I also remember a particularly fun game that I kinda made up on the fly. We had a bunch of guest players begging me to run them through Undermountain. Several guys brought in characters from another DM's campaign.
This next part is something important to keep in mind...
The other DM agreed that
whatever happened in my Undermountain one-shot would remain in effect in his campaign as well. I had quite the reputation back then, and people actually came to me to "learn" how to run Undermountain. And they knew that I ran a very challenging Undermountain campaign. But these were some overly confident old timers who'd all reached their upper teen levels by then (15th to 18th). They wanted the ultimate challenge! They had lots of very valuable and cherished magic items that they worked very hard to get (and to create in some cases).
One of those guys had a wizard who in reality was a lich. He used spells to prevent his rotting and to cover his appearance, etc. Well, the party ran into all sorts of problems even though they were high level. I believe that was the one where Trobriand personally led a gaggle of scaladars to hunt down the PCs.
All their followers died, several party members died, and they escaped only because Halaster (unbeknownst to the PCs) told Trobriand to back off since Halaster wanted to have some fun with these arrogant upstarts.
So the party takes shelter in a secluded room in a very inaccessible area. They decided to dig in and rest for the night, as they were low on spells (virtually no spells left), and terribly injured. They took what healing they could, then rested. They obviously wanted to post a guard, so the lich/wizard offered to stand guard all night. He explained that he had "some magic that allows me to stay awake all night". The others were more than happy to let him do so, as he was 18th level and had proven extremely trustworthy.
Well, Halaster knows the evil that lurks in the hearts of men (and liches!). He has permanent
true seeing, so he knew the guy was a lich. The lich/wizard was with the party only because he had hoped to meet Halaster and petition him to become an apprentice. Well, this lich pissed off Halaster by destroying some trinket that Halaster was fond of, so Halaster had other plans.
He appeared to the lich in the night, since the lich was standing guard outside the door to the room where the other PCs slept. Halaster told the lich that he would teach him of powers beyond his wildest dreams, but that he had to earn the right. Halaster said he wanted to know that the lich would be loyal to Halaster, and Halaster
only!
So he told the lich to go into the room, cast
Mordenkainen's Disjunction on the PCs so that it would destroy their magical items, and that if he did so, Halaster would not only take the lich in as an apprentice, but would also assure him that his fellow PCs
would encounter nothing more small bands than orcs on the way out. Remember that part. Trust me.
The lich went in and cast the spell. In fact, I believe he cast it twice, just to make sure. Well, the PCs are all asleep, and I tell the players to start making item saving throws. Well, it was a disaster! Even the paladin's holy avenger sword failed!
The PCs wake up to find that most of their magic items no longer glow, they cannot invoke powers from any magic items, etc. They're furious! All their items are dead! I think just one or two magic items made it. As they tried to figure out what happened, a magical scene appeared on the wall, as if the entire wall was a crystal ball. It showed precisely what happened that night, it showed the lich admitting to Halaster that he was indeed a lich and that he'd planned all along on selling out the others if he could just convince Halaster to make him his apprentice. It even showed him casting the spell that destroyed almost all their magic items.
Then an image of Halaster appeared and said something like:
"Tsk tsk. With friends like those, you pathetic adventurers don't need enemies."
He then turned to the lich and said something along the lines of:
"How foolish of you to assume I would take someone so utterly repulsive, irredeemably inferior, totally unworthy, and clearly disloyal as my apprentice. You have much to learn, lich, but little time I fear, to do so."
Before fading out, Halaster said:
"I leave you now to work out your differences. Thank you for visiting my humble abode. Oh, and
I lied about the orcs."
Oh man, did all hell break lose! I remember one very incensed player saying:
"Let me get this straight. Everything that happened tonight counts? When we go back to our regular campaign with our regular DM, he's going to enforce the fact that all this happened?"
Yup.
"That [profuse expletives deleted
] is [profuse expletives deleted
] dead!"
Well, that was it! That poor lich quickly learned the pleasure of well applied overbearing rules, he was netted, he was bound, and he was destroyed with the few magic items they had left. It was as vicious an attack as any I'd ever seen.
All that was left of the lich was a pile of broken bones and some scraps. Then one PC who was particularly incensed burned the parts over and over until there were nothing but ashes. The guy playing the lich had a look of "deer in the headlights" during the entire time, as he couldn't do anything! Then he claimed that he had some sort of regeneration powers. So the incensed PC said that they'd carry the ashes with them and keep burning them forever if need be.
Then the lich player said "Well, you'll never know where my phylactery is, and as long as that's intact, I can always come back."
As it turns out, the lich had left his phylactery buried in a cavern in one of the areas in Undermountain, with some dead bodies nearby, in case he needed to come back in just such an occurrence. His plan was to kill whatever party members survived on the way out, and that if anything happened to him he could simply go back into his phylactery and usurp one of the dead bodies nearby. That way he'd be back where he wanted to be...in Undermountain learning from Halaster.
Well...
Halaster used telepathy to tell one of the PCs about "something that belongs to your lich friend that he left behind" or something like that, and they got their hands on it and destroyed it. Poor lich!
Oh man, the other DM laughed his ass off! He'd been trying to get rid of that lich for some time.
My reputation for the capacity to be utterly cruel was cemented with that game.
) had set in a particularly devious trap. It was either on Level 2 or 3, I forget which. 
