Once the party arrives at Shardpit, the first major building they'll bump into is the stables. Like almost every other building in Shardpit, its elevated (1 square) on thick posts, but otherwise looks "normal". However, normalcy isn't something I'm going for here, so I want the town to appear normal in every way with the exception of a minor detail or two.
Liiike, empty streets. They don't see anyone. If they approach the stone in the middle of the path, they will discover that it merely points out the most direct (and safe) route to the House Tharashk enclave (north). A moderate Perception check reveals blood on it despite the rain.
Shortly after continuing on, characters with a passive Perception of 10 or higher automatically notice dead horses in the stable yard. If they investigate, an easy Heal check reveals that they were bludgeoned to death despite the fact that they were also eaten. A moderate Heal check reveals that the bite marks are human in nature, and that the horses have been dead for about two days.
At this point, characters with a passive Perception of 17 will hear something growling from inside the stables. If they investigate the stables, they find that the gates have bloody hand-prints on them, blood stains the hardwood floor, and several pens have dead horses as well. In the last one, they find a stable-hand eating a freshly clubbed horse (the bloody shoeing hammer is on the ground next to him).
Now, if the players just barge on in and make a lot of noise, the stable-hand instead tries to ambush them. His Stealth isn't that hot and I figure the best I'll get out of it is having him take a swing at the first person to look into the pen he's feeding in. That's okay, because I want to surprise them since I'm hoping that they keep thinking back to the Epilogue session where they controlled random NPCs fleeing from something that they couldn't ascertain. Excepting from his extra mouth, the stable-hand also isn't anything too fancy (level 1 skirmisher), so once combat begins the noise attracts other townsfolk who come-a-callin'.
Most of the everyday citizens dont suffer from any extreme mutations, though there are exceptions like the poor, poor stable-hand (I think I'm going to say that those who are in possession of treasures taken from the shrine are at high risk of contamination). His slobbering maw is a shark's mouth and grows from his stomach. He seems to go into a frenzy at the taste of blood.
Human rabble will fill the niche I need for rushes. Most of the humans in Shardpit look perfectly normal, except for a deranged look in their eyes. They are all very dirty and smelly, having spent the last few days reduced to an animal-like state. They tend to cluster together with a pack mentality, avoiding the townsfolk that possess major physical deformities. Their stat blocks dont need any change.
Guards were sent into the shrine to investigate it for traps and monsters. Since they all share the barracks, they infected eachother and now possess tentacles growing from some part of their bodies. Their fingers have begun to grow suckers and bond together, and their skin has become splotched.
Along with the guards went the hounds. Again, they share a kennel and have some shared features: guard dogs have chitinous growths and spines (emphasizing the soldier role better), while the hounds just have multiple sets of eyes. Down here, they all teleport.
Thinking of changing the names, but frankly I don't care too much since the players wont see the names: I just want a normal dog and then an armored one.