Their Origin:
The angels were all created by God as a great host of sinless spirit-beings, most of whom kept their first estate of holiness and presently worship God and serve His purposes (Psalm 91:11, Psalm 148:2-5; Matt 18:10, Matt 26:53; Luke 20:36, Col. 1:16; Heb. 1:4, 14, 13:2, 1 Peter 1:12).
The Fall of Some:
One of the angels, Lucifer, fell through the sin of pride, thereby becoming Satan, and influenced a large company of angels to follow him, who thereby became demons (Isaiah 14:12-17; 1 Tim. 3:6; James 2:19; 2 Pet. 2:4).
Satan's Work:
The work of Satan and the demons is the attempted subversion and supplanting of the work of God. By a subtle suggestion, Satan accomplished the moral fall of Adam and Eve, subjecting them and their posterity to his own power (Gen. 3:1-7; Job 1:12, 2:6; Ezekiel 28:13 -15; Zechariah 3:1-2; John 8:44; 2 Cor. 4:3-4; Eph. 2:2). Satan continues as the enemy of God and the accuser of God's people and persistently seeks to counterfeit the works and truth of God (2 Cor. 2:10-11, 11:13-15; Eph. 6:12,16; 1 Pet. 5:8; Revelation 12:10).
We believe that Satan was judged at the cross, and that at the second coming of Christ, Satan will be bound and cast into the abyss for a thousand years, and after the thousand years, he will be loosed for a little season and then the judgment will be executed by his being “cast into the lake of fire and brimstone,” where he shall be tormented day and night for ever and ever (John 12:31; Col. 2:15; Heb. 2:14; Revelation 20:1-3,10).