The details you get on the bog imps before you leave, as you are discussing what might be out there are from a collection of soldiers. They tell you that the swap fey can make anyone sick with their attacks, bite and claws. The imps can cause any water to turn noxious and fetid. They are can hide anywhere in the swamp and are immune to a wide variety of spells. They are small but quick and have no problem moving on land, in the water, or through the trees. Worst of all, they can make any even small puddle turn into a deep pit of water.