Lest Satan should get an advantage of us: for we are not ignorant of his devices. 2 Corinthians 2:11
He is Satan; cunning and crafty. He is a spirit, but he also has attributes of a real personality. His goal was to become as God and when that plan failed, He purposed to destroy all that God holds dear. His hatred for God extends to those who love and follow God. Satan unleashes all that He has in his arsenal to prevent us from believing and following God. Jesus warned Peter of this fact:
Be sober, be vigilant, because your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour. (I Peter 5:8)
Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world. 1 John 4:4
For those who believe in Jesus, Satan is already a defeated foe
. . . and he is only able to overcome a believer as they yield control to him.
Because Satan is not omnipresent (present everywhere), he dispatches a host of demons throughout the earth to do his will and accomplish his purposes.
But every believer; every saint of God, ought to know that greater is He that resides within us than he that is in the world.