jackattack wrote: ↑
Mon May 08, 2017 10:02 pm
I'm not sure what kind of encounter or scenario you have in mind, but here are some ideas.
Rats. First they are here and there, darting out of sight as the party approaches. Then there are more of them, and they just watch as the party goes by. Then the party realizes that the rats are following them in ever-increasing numbers, but if the party approaches they draw back. Eventually the party comes to a large chamber or cavern and finds all of the passages blocked by swarms of rats, who stand their ground if the party approaches but do not advance on the party. Finally, the rat swarms enter the chamber and surround the party, giving way to the giant/dire/fire/whatever rats coming through the passages to kill the party.
Rat swarms that seem to be charging the party, but then pass them by, are good indicators that something very bad is coming.
Stirges. Annoy your party with apparently random stirge attacks, and make sure the stirges at least try to get away when they take damage. When a couple-few have flown off, tell the party they hear whispering, then rustling, then fluttering, then fill the tunnel with stirges looking for a snack. Hiding under the water (CON roll or WILL save to stay under?) allows the swarm to go by without attacking. Have the swarm go by a couple-few times, then while the party is in a dry room or cavern have three or four swarms converge on them at once.
Leeches. As the party wades through the sewers, have them make perception checks to realize they are picking up leeches. Allow them to burn or salt or magic the leeches off, but as they go further give them more and bigger hitchhikers. Eventually they should get the idea that they are headed for a giant leech encounter.
If the party is stopping to make perception checks, have very high and very low rolls result in the characters seeing shadows move or hearing splashes in a random direction. If they investigate, they find nothing. If they stop making perception checks, something jumps out to kill them. If they start trying to disbelieve, let successful rolls dismiss their perceptions as random imaginings -- BUT if they perceive something real and roll to disbelieve, let the characters "convince" themselves it is nothing just before it jumps out to kill them.
Harass them with mysterious wakes in the water. They see a wake cross an intersection ahead of them. They see a wake moving away as they approach. Finally the see a wake headed their way, but it vanishes before it gets to them. (Or, if they get out of the water and prepare to defend themselves, it goes by.) The wakes might mean nothing (just random sewer critters) or they might eventually be a precursor to an encounter.
Allow opponents to use the terrain to their advantage. Got lizard men? Allow them to make stealth rolls to hide underwater, and REFLEX saves to avoid being stepped on as the party wades past. Then enjoy the looks on the players' faces when they realize they are surrounded.
That's what I've got off the top of my head. Hope any of it is useful, or gives you a better idea.