The word demon derives from the ancient Greek daimon (a spirit or divine power), and does not carry the negative connotation the modern word has given the term in its appropriation of it. With the passage of time, demons gradually became seen as evil spirits, fallen angels, or spirits of unknown type that can possess a human soul. The list of the 25 Scariest Creatures in Myth and Religion that follows will help you understand why so many people fear these demonic beings. Interested in learning about more creatures? Check out 25 Mythical Creatures That Never Existed But People Believed In Anyway. If you enjoyed this list, you may also enjoy 25 Craziest Mythical Creatures Ever Conceived.