Fear moss

Fear moss was a type of solitary predatory plant which would hang above water holes and cover mammals that came near, so as to live off their bodily fluids. It enjoyed the adrenaline and other chemicals that frightened animals produced, so it secreted a type of poison to ensure that it could consume these. When a Force-sensitive creature was affected by this poison, it would lose control of its fear and drift closer to the dark side of the Force. Such dark side creatures were particularly appealing to the moss, as it could taste the increased fear that they had. Fear mosses were Force-sensitive, being able to sense those who came near; they could detect Force-sensitive beings from dozens of meters away. Force-sensitive beings felt unnatural fear when close to fear moss, even without being poisoned.

Text and facts from the “Fear moss” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.