As the party sits at a local tavern, a Mastiff bursts through the door, its Halfling owner running close behind. It appears as though the mastiff has something in its mouth.
The mastiff is wily and moves under tables and around patrons, not wanting to give up whatever it has in its mouth. It is able to be corralled if the party opts to use Animal Handling DC12+ or if they decide to use some magic of some sort to dissuade the doggo from running further.
Once stopped, everyone in the tavern is able to see what the precocious pooch has in its jaws, a Slaad Tadpole.
“Greebs! You drop that creature right now!” yells the owner. “Where did you get this?” The Slaad Tadpole bites the owner, who proceeds to drop it, giving opportunity for the mastiff to scoop it up and sprint away out of the tavern.
If the party asks the owner, who identifies himself as Blerben Bigglefoot, what is going on he’ll explain that he and his dog were playing fetch when he accidentally threw the ball over the fence and into their neighbors yard. The neighbor has been acting a bit odd lately, and seems to have forgotten how to speak, but was very upset about this tiny creature that the dog took. If the party mentions that the creature is a Slaad Tadpole, Blerben has no idea what that is, but is happy to take the party to roughly where Greebs found it.
Following the trail of Greebs, Blerben escorts you to his home, a little under-hill home with a fence line that cozies up next to a small cottage near a swamp.
Greebs is still running around in the yard with the creature, being careful not to hurt it, but completely unwilling to return it to Blerben. As Greebs and Blerben run around in the yard (the party is welcome to assist again), the neighbor comes outside and begins to screech from the fence line. The screeches sound like someone attempting to mimic Common, but having no idea how the syllables are put together.
The neighbor appears humanoid in form, but its eyes bulge a bit more than usual, its skin appears slimy, and mannerisms appear off. The party could use Detect Thoughts, Suggestion, or if someone has Truesight, they can determine that the neighbor is actually a Green Slaad.
However it comes to pass, the neighbor begins to get more and more agitated with the dog unless the party or Blerben are able to get the Slaad tadpole out of its mouth. If no one helps and the dog continues to run around, the neighbor will suddenly cast Hurl Flame at the dog, attempting to get it to drop the tadpole.
If the party is displeased by this (boy, we hope they are), roll for initiative.
DM Note: The Green Slaad hit its one hundredth year of life and is attempting to transform into a Gray Slaadi, though it had trouble doing so in Limbo. It is in this particular plane in order to determine how best to accelerate its transformation. It is accompanies by a small contingent of Slaadi including two Red Slaad and two Blue Slaad. More on Slaad here, but in this scenario, the Red Slaadi was able to hatch one of its offspring, which the dog then ran away with. The Red and Blue Slaadi have no shapechange ability and are currently in the basement of the home, waiting for for passersby in the night to claim human hosts. If left to their own devices, the group will take over the town over time, spreading chaos throughout the realm.
If able to get the tadpole back to the Green Slaad, it will return into the home and all will be well enough. A portal to Limbo in the basement will stay open unless closed by the party, and that can only be done once they have eliminated or incapacitated the four basement dwellers.
Slaad Be With You Til We Meet Again
The neighbor will change shape back into Slaad form as the fight begins, horrifying Blerben who runs and hides. Greebs also yelps at the flames, dropping the Slaad Tadpole and hiding with Blerben.
Throughout the fight, the Green Slaad will attempt to reason with the party through telepathy, explaining the situation. They only need a few human hosts in order to continue their research and they will let the party live if they turn a blind eye to what is taking place.
The Green Slaad will attempt to set lots of fires, potentially turning his magic toward the house in order to bury the portal to Limbo they created.
DM Note: Red Slaad Claw attacks on humanoids trigger a DC14 CON saving throw, otherwise they implant a tiny slaad egg into the creature. It takes three months to gestate, but will kill the host if it goes to term. The implanted egg can be treated as a disease in terms of the healing process.
Blue Slaad Claw attacks on humanoids trigger a DC15 CON save or they are infected with a disease called “chaos phage.” If reduced to 0 HP, the humanoid instantly transforms into a Red Slaad or a Green Slaad if they are a spellcaster.
If the party inspects the home, they will unfortunately find the neighbor’s body there, as well as the portal in the basement unless the house is reduced to rubble. If they do not close the portal, more Slaadi will come through over the next few days, resetting the whole cycle.
Rewards here are up to the DM, but possible that if the party talks to the mayor or leader of the town about the Slaad infestation, they will get some sort of gp reward for their assistance.