Devil means evil. Evil is always there with Good, but we call it "devil." Anger, greed, jealousy, hatred, lusts, pride, inferiority complex, these are all the devil. Therefore anyone who has these characteristics is a devil to that degree. Man has both divine and devilness in him. So the devil does not have any religion. The devil is not to be looked upon as a person like Ravana or some power that will destroy us. The devil is these characteristics of lust, greed, etc. Ignorance is the greatest devil of all. So the devil exists in that respect.

-- Swami Radhanandaji