Demons in a dream are a symbol of ignorance and negative habits within one's own life zone. Very often they also mean fear, emotional or physical abuse.
see - the secret you are hiding will become a nightmare for you
see - watch out for false friends who will try to mess you up under cover in life
to be possessed - suppressing your own desires and needs will not be good for you in life
defeat the demon - overcome your own weaknesses and you will achieve the planned success.
More dream interpretation: