Our opponent

"Be sober, watch : your adversary, the devil, like a roaring lion, prowls around you, seeking to devour." 1 Peter 5. 8

"The devil who had misled them was thrown into the lake of fire and brimstone ... where are the beast and the false prophet ; and they will be tormented day and night, for ever and ever." Revelation 20. 10

It is the tempter and the seducer, the devil who tempted Eve and made her and Adam fall into sin. He tempted the Lord and sought to seduce him, but he found no fault in him who always answered him by the Word of God.

It's the devil (the slanderer). He is basically the one who creates the division where the unity is, which introduces the dispute where the harmony is.

He is the liar. He speaks lies, because it is in his nature. He draws it "from his own funds" because he is "the father of lies" (John 8:44). He's the murderer. "He was a murderer from the beginning" (John 8:44). The greatest crime he has committed is the death of Jesus on the cross. But in this act he suffered a final defeat : he could not turn from obedience the man Christ Jesus who was perfectly devoted to God.

He is the leader of the world (John 14:30), the god of this age (2 Corinthians 4: 4). Satan is the origin and the inspiration of all the evil that men do on earth, but of which they remain responsible before God. He dominates over all who do not recognize the authority of God.

He is also the accuser of the brethren (Revelation 12:10), the redeemed of the Lord whom he can not bear and whom he seeks to turn away from God. Fortunately, the perfect justice of the Lord covers his people ! We remember when Satan accuses us of ourselves to make us believe that we are not good enough Christians to be loved by God !

Originally Satan was a magnificent angel and he still possesses a formidable power ; yet he remains a creature, so he will not have the last word. He still plays his role in the divine plan as long as God's patience with men lasts ; but, following his defeat at the cross, he will disappear from the scene and undergo an eternal judgment.

It is to Jesus Christ, the Lord, that authority over all creation in heaven and on earth is an authority which he will soon establish in a perfect manner.

Source (Pleasing the Lord)