Note: Minor spoilers for BfB
My PCs are currently slogging their way through the Hooktongue swamp and as I've done for previous books, many of the "random" encounters are in fact planned out ahead of time so they flow a little better. After rolling an encounter with 3 hags, I was trying to find the best way to incorporate them and here's what I came up with:
The Setup:
First, I changed the fixed encounters somewhat so that the refugees were in fact a group of traders who had taken something of a wrong turn coming up the East Sellen River and had a run in with a rather irrate Hydra. After the PCs discover the wreck of their boat (and defeat the 12-headed monster), they quickly find some of the survivors not far away.
The Hook:
The hags have been picking off stragglers from the wreckage for the last couple days as a bit of fun though the source of the threat is unknown to them. Once the PCs start leading the group to safety (in the same day they found them) they hear the screams of one of the survivors in the distance. When they rush to investigate they find that one of the women from the group is quickly sinking in a large patch of quicksand while a pair of will-o-wisp watch on in delight.
The Trap:
When the PCs go to rescue the woman and/or dispatch the will-o-wisps they discover that things are not exactly as they seem. The will-o-wisps are in fact a simple dancing lights spells and easily serve to waste a couple PC spells. If a PC manages to reach the flailing woman, she drains their strength with her touch attack since she is in fact a hag. The confused PCs are then confronted with the "real" threat of the encounter in that two medusa make themselves known from behind some trees at the far side of the quicksand and assail the PCs with various spells (baleful polymorph is how I started, turning an eidolon into a butterfly).
The Truth:
The medusa are, of course, the other two hags. All three of them are disguised using a veil spell. The quicksand isn't actually real either and rather just a pool of water that the third hag is swimming in, disguised by mirage arcana. It is particularly amusing (to me as the DM, anyway) at this point when PCs try to close or avert their eyes while fighting the medusa since it gives them a pretty decent advantage when trying to drain strength from their victims and eventually grapple and drag them underwater. Once one goes down, however, the other two try to turn invisible and run (and then pester the PCs again in the future).
The Aftermath:
All in all, the PCs had fun with this one despite being perplexed at the time. One PC had a good amount of strength drained and the eidolon was turned into a butterfly but the came out victorious. They were never in that much danger (being only a CR 9 encounter) but they didn't *know* they weren't in danger which added to the fun. Just thought I'd share in case people wanted to snag this sort of thing for their own campaign.
