Consciousness Stealer

"The Helcionelloida, an ancient creature that existed five hundred million years ago, went extinct about four hundred million years ago. It's the oldest known conchiferous mollusk.

"This creature lives deep undersea and due to the timeframe of its existence, humans' understanding of it largely stems from its resulting fossil structure. Based on known fossils, humans infer that this kind of creature should be hermaphrodite and don't need to mate to reproduce. Furthermore, they are born with a unique paired nerve that doesn't contain a dedicated nerve center. This unique implementation enables the nerve tissues to survive even if the muscle tissue perishes.