We must put on the full armor of God to stand against the demonic principalities, an army of 1/3 of the angels, bent on the destruction of God's elect.
The spirit in man is initially good, but capable of being influenced by the spirit of this world, and surcharged with Satan's negative attitudes.
Satan works on us through our imagination; he broadcasts images to our minds. To counter this, we must resist him, practice humility and draw close to God.
The origins of our adversary, Satan the Devil, and his host of fallen angels or demons. God has promised us protection if we yield to and obey Him.