The party arrives in a town where the air is thick with sickness. Townsfolk clamber through the street, coughing up pink and purple clouds as they go. A medicine check will reveal that they have come down with some sort of disease that is plague-like and passes from person to person through any sort of physical touch.
If the party doesn’t leave immediately, a frantic tabaxi cleric approaches them for help. Identifying himself as Mr. Meowmers, he explains some of the situation.
“I’ve dedicated my life’s work to tracking down the cause of this ailment. I’ve seen it too many times and believe I have a way to prevent the spread, but no one will listen to me! This cootie plague will be the end of the realm if we don’t stop it.” He coughs up a hairball apologetically. “It is caused by an aberration that picks one victim and then lingers to watch the spread. Any touch, and the affliction takes hold. After one month, those infected explode into piles of pink and purple clouds.”
The blood domain cleric sobs as he continues, “I attempted to warn this town last week and give them immunity, but only one family listened.” In the distance a man walks past, unaffected, and waves at the party. He quickly sprints away as several infected chase after him.
Mr. Meowmers frowns and says, “I have reason to suspect the creature responsible is headed for [next town over], and is hiding in the old abandoned windmill just outside of town.” He is planning on going to the next town over, but before he does, offers the party the immunity of which he spoke.
If the party agrees, he will grab their wrist, rub some purple powder across their arm and make some circular marks in the powder while reciting an incantation. “Circle, circle, dot, dot, now you have your cootie shot. Safe from plague, and malevolency, now you have immunity.” He withdraws his paws and blows the powder away, off the wrist and into the face of the “patient,” revealing glowing purple and pink runes on their forearm. He proudly examines his work and smiles at the party.
“One more thing, if you can bring back some of its fluids, I might just be able to make a cure.” The elderly tabaxi slinks off to the next town, seeking to prevent another mass outbreak.
To The Windmill, to the Wall
To locate their target, they must employ their investigative skills and knowledge of nature as they track it across challenging terrain, or they can just ask where the abandoned windmill is.
As they approach, they see tracks leading to the windmill, and notice a small creature jumping around on the path. It is fuzzy, cute, and appears to have no malicious bone in its body.
If the party approaches, it remains docile, even curious, and begins to wobble between the legs of the party, babbling and laughing as it does so. After a few rounds of running between the legs, or if attacked, the little beast will pause by a leg, open its maw wide revealing rows of jagged teeth and attempt to bite down on the nearest leg.
Any bite by this creature oozes with pink slime, but if the party took on the runes from Mr. Meowmers, the Contagious Bite does nothing and no saving throw is required. After the first hit on the creature, five to ten more will appear from in and around the windmill.
As soon as half of the creatures are dead, the party will hear a loud roar from inside the windmill. Emerging is a medium aberration, with a much more fearsome exterior and no laughing at all.
This is the Cootie Monster that Mr. Meowmers warned the party about. The monster roars and immediately jumps into the middle of the party using its Invisible Ambush attack. The remaining Cootie Monster Minions all cheer and spend a bonus action dancing in appreciation of their leader.
DM Note: You can force the party or monster back inside the windmill for more close quarters combat, where you could also unleash a few more minions if you so desire.
If the Cootie Monster is killed, it will begin to convulse and after 30 seconds will explode into clouds of pink and purple, the same demise those ailed with its plague have also met. At this point hopefully the party took some blood or fluids from the Cootie Monster prior to it exploding, otherwise the party will have to look inside the windmill where they can find some slime on the staircase, but no blood. Any removal of a body part will keep it in that form instead of turning into clouds.
If any of the minions are still alive, they will become enraged and their speed will double. Similar, their bite damage will double as they chomp down with eyes full of tears. If the party leaves the area, any remaining minions will give chase until they are defeated.
When the party meets with Mr. Meowmers at the next town, they will find him being dragged away by the town guards. The party will need to find a way to persuade the guards and the mayor of the town that he is trying to help (if any of the cootie monster body parts are kept, that makes it pretty convincing).
If released, Mr. Meowmers will use any remaining fluids to concoct a potion that he can give to townsfolk in the next town. Up to the DM as to how effective that is to those who contracted the plague, especially depending on the fluids the party collected.
If he is not released, Mr. Meowmers will thank the party for their work, but tell them he believes the Cootie Monster always comes as a pair, so if they only defeated one, there my be another out there. He has no proof, but he fears the plague may continue if he remains stuck in jail.
Regardless, he will hand over an Amulet of Lesser Restoration, that gives the wearer the ability to cast Lesser Restoration once per long rest.
If you like the concept of townsfolk exploding into something strange, be sure to check out Penny For Your Dots.