1. White Plume Mountain
Neverwinter. Mount Hotenow: the sleeping volcano has begun spewing up white plumes for the last two weeks. By the time you arrive in the city there's a constant fog that limits visibility to 100'. It also gives mortals a bad cough, but you're made of stronger stuff.
You spend Mirt's coin on whatever extra equipment seems wise to you; and knowing most of you, you spend quite a bit on a great time in Neverwinter's finest tavern. Ahhhh, Neverwinter Nights.
Finally it's morning and you set up into the mountains to locate the entrance to Keraptis's dungeon. Following instructions provided by locals who have no reason to lie to you, you arrive by 4pm at the Wizard's Mouth:
This cave actually seems to breathe, exhaling a large cloud of steam and then slowly inhaling, like a person breathing on a cold day. Each cycle takes about 30 seconds.
Supposedly the volcano continues up another 2000' feet to the cone, but you can't see it. You can't see the sky. Only the white plume. You heads feel the cold August air, while your feet feel the warmth of the molten lava just below the earth.
The cave is about 8 feet in diameter and 40 feet long. At the end of the cave, near the roof, is a long, horizontal crevice about a foot wide. The air is sucked into this crack at great speed, creating the loud whistling noise and snuffing out torches. Shortly the rush of air slows down, stops for a couple of seconds, and then comes back out in a great blast of steam. This steam is not hot enough to scald you, but it does make the cave very uncomfortable, like a hot sauna bath interrupted by blasts of cold air.
The ceiling and walls of the cave are slick with the condensed steam that runs down them. The floor is covered with several inches of fine muck. The one among you with the highest Passive Perception searches the mud and finds a small trapdoor with a rusted iron ring set in it.
Now what?