My players are currently travelling north through the Underdark from Mithrall Hall. They have hired a guide to lead them to an exit close to a lost shrine of Shaundakul. The guide is competent and is a Prime Underdark Guide.
Last session, the PCs entered the underdark and were warned by a dwarf captain on duty with his soldiers that Drows were forming an army to the east (they come from Menzoberanzan, they are headed for the Battle of Keeper's Dale). The guide told them not to worry as they were heading north and no scouts had been reported there. After a day of travel they encountered a chasm and some rat swarms, they saw some weird environnement, a PCs almost died when moving a corpse that had toxic gas inside and they fought some Duergar Slavers that had fled Mithral Hall when the dwarves drove them out.
So I'm looking for challenges that will really show them how the underdark is a cruel and weird twisted place.
The travelling time to the exit they are looking for is about two days so I'm looking for meabe 3 or 4 encounters.
So I'm wondering if any of you guys had any encounter ideas. I thought about some Ooze, Hook Horrors and meabe a drow scout patrol... But I don't want to implicate the Drows too much. The PCs fear them and I think that this fear is from the fact that they have never seen any.
I'm asking the Wizards board as I know that you guys have always the best ideas when it comes to creative stuff like this!
Thanks a lot!
Monster's of Faerun is an excellent resource for running Underdark encounters, as it contains several creatures that can be found there: Beholderkin, Deepspawn, spider swarms and monstrous spiders chief among them.
Since you want to avoid Drow, I would suggest Illithid Slavers. Instead of just rolling for surprise and running a standard encounter, what I'd do is have the party come upon the illithids right as one or a couple of them are sucking the brains out of wounded dwarves. The other illithids are holdding several other dwarves in thrall--these dwarves are mostly healthy and not wounded from battle--with their mental powers and are prepairing to lead the dwarves away (think of it as a pre-trip snack for the illithids).
Another encounter could involve a pair of advanced Ropers who lure unwary travelers into patches of quickstone.
(Quickstone is the Underdark equivalent of quicksand: it looks like natural stone but quickly swallows up anyone foolish enough to step into it. The DC to attempt to get out of quickstone are increased by 5 from what's listed in the DMG for regular quicksand.)
The Ropers attempt to attach tentacles to obvious spellcasting PCs at maximum range. They depend on melee PCs moving in by foot to attack them up close, as they've positioned themselves behind a large patch of quickstone.
If your party are already flying about via rings or other magic, you can always make the ceilings in the tunnels they're traveling in very low in order to restrict movement and funnel the party into danger (like the waiting Ropers).
Hope this helps!
You can also create locations with stale air or even no air that are caused when earthquakes and cave-ins expose pockets of gas and vapor that haven't circulated for years or centuries or create pressure imbalances that suck all the air out of a tunnel.
Stale air can weaken PCs who fail Fortitude saves. For areas of no air you can use the suffocation rules in the DMG.