Demons are used by satan to oppose God, His plan and purposes, and His people. They also war against unbelievers to keep them from the truth of the Gospel.
Demons control specific territories (principalities) such as the prince of Persia mentioned in Daniel 10:12-13.
Demons also work through personalities - through men and women - to accomplish satanic objectives in the world.
Opposition to God's will is satan's main objective. The word "satan" means "adversary." Satan is primarily God's adversary (Job 1:6; Matthew 13:39). He is secondarily man's adversary (Zechariah 3:1; 1 Peter 5:8).
Demons have different natures.
One demon identified himself in 1 Kings 22:23 as a "lying spirit." A "deaf and dumb" spirit is identified in Mark 9:25.
Demons of various natures operate as spirits of infirmity, seducing spirits, and unclean spirits. Satan uses them to war against man in body, soul, and spirit:
