Other monsters.

Anything that doesn't have a category yet.

Where these things come from and more specific stuff is a mystery. As nobody can stand being around them for very long. Most people succumb to the spoilers.

(Literal fourth wall breaking spoilers. For example: 'shashashaSoylentgreenispeopleshashasha' and sometimes spoilers for the RPs like the one that said someone in the current adventure party would die. That last one has been haunting the players and NPC members ever since they heard it.)
While attacking they slap their target. They're also very hard to damage as things tend to bounce off them.

They are always in group. Just as I said earlier anything else about them is a mystery. (Which will be explained eventually.. when I finish studying the specimen in my backyard.)