"Gak! Cough! I just swallowed a bug."
Spiders of the moonlight, weaving webs of smoke, mist, and moonbeams.
Sometimes, someone is watching in the middle of the night.
Rats the size of cats, these insectivores are tree-top hunters. While they are useful to farmers and people, they are considered pests.
It is whispered at harvest bonfires that sometimes swarms will combine into a monstrously huge pile of Black Leaf Bugs, able to instantly stop anything it comes across. What is left explodes in a shower of maggots.
There is a land where every person wears spectacles. Those without eyeglasses are considered to be the lowest stratum of society, so adventurers without glasses are treated like outcastes. It certainly would explain those heroes wearing sunglasses for no apparent reason...