Demon
The contemporary Roman Catholic Church unequivocally teaches that angels and demons are real beings rather than just symbolic devices. The Catholic Church has a cadre of officially sanctioned exorcists which perform many exorcisms each year. The exorcists of the Catholic Church teach that demons attack humans continually but that afflicted persons can be effectively healed and protected either by the formal rite of exorcism, authorized to be performed only by bishops and those they designate, or by prayers of deliverance, which any Christian can offer for themselves or others.
International Association of Exorcists
Although the membership is restricted and exclusive, by 2000 there were over two hundred members, who meet bi-annually in Rome. The association sends out a quarterly newsletter where members can tell of particularly interesting or difficult cases. An exorcist priest must have the permission of his bishop to join. 
Within the Roman Catholic Church a priest may only do an exorcism with the express consent of his bishop or local ordinary, and only, to the extent necessary, after an examination of the patient by doctors and psychiatrists in order to determine that the affliction has no natural origin. A priest is required by canon law to be devout, knowledgeable, prudent, and possess integrity of life.