|“||Don't you see? You're nothing more than imaginary creatures I created in my mind!||„|
|~ Frederic Francois Chopin about to betray his friends in his "dream".|
These are the villains that are not physical but rather exist in the astral realm (though they may be able to possess others). Alternatively, they may not be real beings at all but psychic energy given life (or the illusion of life) by some powerful force. Sometimes they are simply created inside a real character's mind and only exist within their heads.
From imaginary friends like Tyler Durden to beings that act as people's nightmares (such as The Grand Duke of Owls), these beings, while not real creatures can create a strong mental challenge by making real characters and possibly the audience unable to tell the difference between what's real and what's not real.