Symbolic of evil spirits, 1 Cor. 10:21
The darker side of the spiritual realm, a demon is a being that feeds on fear and hatred. When a demon appears in a dream, you are being put on notice that your shadow side is out of control and things that are sparking fear are getting the better of you.
A demon can also be an indication that you have been ignoring a destructive pattern for a very long time.
Evil spirit; revealing one’s problems are spiritual not carnal; see “spirit” and “witchcraft”
Although the word ‘demon’ originally came from the greek word for ‘deity’, for many hundreds of years it was taken simply to mean spirit. In the modern day it is taken to be an evil spirit, one at odds with god, and has this meaning in dreams.
Psychological / emotional perspective: Psychologists now believe that demons in dreams are often personifications of deeply held or ingrained fears.
The colour of the demons will often give information as to their relevance. Red indicates extreme and black might represent fear.
Material aspects: Passionate beings with their own agenda, demons may represent a particular type of personality that will not allow itself to rest until a task is completed.
Depth Psychology: Dreaming about demons usually refers to feelings you are denying, but that have, nevertheless, taken hold of you. See Aggression, Disgust, Envy. Frequent dreams about demons are warnings: make an appointment with a psychotherapist in order to avoid future emotional conflict and/or crises. See Devil, Monsters, Mystical Creatures.
The image of the devil in a dream (whether he has horns and tail) indicates that you should not be tempted to use illegal means in order to achieve your goals. It means that you are in an obscure, hidden situation, or that you have a double intention. In addition, the devil can impersonate your fears, desires that you repress, or some misconduct in real life. The best weapon against the latter is to make use of love and honesty.
The figure of Satan appears in the Jewish, Islamic, and Christian traditions. Originally, it represented fertility and the powers of nature. Maybe your unconscious is giving you the keys (compost) for your inner growth.