No, not in any objective sense. Things can exist in our imagination and seem very real. This is what we might call 'subjective' reality. We can even indoctrinate others into sharing our subjective reality. If I say the words 'Frankenstein's monster' we all share very much the same image, even though it isn't real. Other people have passed on their concepts of demons, fairies, leprechauns, fairies, angels, devils, pixies and the like. We have an idea of what these things are supposed to look like and what their nature is even though no one has ever seen one. There is no evidence whatsoever for their existence and no reason for their existence. They are not objectively real. Like so many other things, they exist only in the imaginations of those who believe such things.