Satan
And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him. Revelation 12:9
"Man, Sir," I say, "is eager to keep the commandments of God, and there is no one that asks not of the Lord that he may be strengthened in His commandments, and be subject to them; but the devil is hard and overmasters them." "He cannot," said he, "overmaster the servants of God, who set their hope on Him with their whole heart. The devil can wrestle with them, but he cannot overthrow them. If then you resist him, he will be vanquished and will flee from you disgraced." Hermas (A.D. 150) Ante-Nicene Fathers vol.1 pg.29
"But I, the angel of repentance, say unto you; Fear not the devil; for I was sent," said he, "to be with you who repent with your whole heart, and to strengthen you in the faith." Hermas (A.D. 150) Ante-Nicene Fathers vol.1 pg.30
If you turn unto the Lord with your whole heart, and work righteousness the remaining days of your life, and serve Him rightly according to His will, He will give healing to your former sins, and you shall have power to master the works of the devil. But of the threatening of the devil fear not at all; for he is unstrung, like the sinews of a dead man. Hermas (A.D. 150) Ante-Nicene Fathers vol.1 pg.30
I know that you will crush all the power of the devil, and we shall be masters over him, and shall prevail over all his works. Hermas (A.D. 150) Ante-Nicene Fathers vol.1 pg.30
"As many," said he, "as wrestled with the devil and overcame him in their wrestling, are crowned:" these are they that suffered for the law. Hermas (A.D. 150) Ante-Nicene Fathers vol.1 pg.40
For among us the prince of the wicked spirits is called the serpent, and Satan, and the devil, as you can learn by looking into our writings. And that he would be sent into the fire with his host, and the men who follow him, and would be punished for an endless duration, Christ foretold. For the reason why God has delayed to do this, is His regard for the human race. For He fore-knows that some are to be saved by repentance, some even that are perhaps not yet born. Justin Martyr (A.D. 160) Ante-Nicene Fathers vol.1 pg.172
And though the devil is ever at hand to resist us, and anxious to seduce all to himself, yet the Angel of God, i.e., the Power of God sent to us through Jesus Christ, rebukes him, and he departs from us. Justin Martyr (A.D. 160) Ante-Nicene Fathers vol.1 pg.257
For when He became man, as I previously remarked, the devil came to Him - i.e., that power which is called the serpent and Satan - tempting Him, and striving to effect His downfall by asking Him to worship him. But He destroyed and overthrew the devil, having proved him to be wicked, in that he asked to be worshipped as God, contrary to the Scripture; who is an apostate from the will of God. For He answers him, 'It is written, You shall worship the Lord your God, and Him only shall you serve.' Then, overcome and convicted, the devil departed at that time. Justin Martyr (A.D. 160) Ante-Nicene Fathers vol.1 pg.262
And at that time, indeed, the apostate angel, having effected the disobedience of mankind by means of the serpent, imagined that he escaped the notice of the Lord; wherefore God assigned him the form and name [of a serpent]. But now, since the last times are [come upon us], evil is spread abroad among men, which not only renders them apostates, but by many stratagems does [the devil] raise up blasphemers against the Creator, namely, by means of all the heretics already mentioned. Irenaeus (A.D. 180) Ante-Nicene Fathers vol.1 pg.462-463
It is therefore one and the same God the Father who has prepared good things with Himself for those who desire His fellowship, and who remain in subjection to Him; and who have the eternal fire for the ringleader of the apostasy, the devil, and those who revolted with him, into which [fire] the Lord has declared those men shall be sent who have been set apart by themselves on His left hand. Irenaeus (A.D. 180) Ante-Nicene Fathers vol.1 pg. 523
So likewise also the devil, being one among those angels who are placed over the spirit of the air, as the Apostle Paul has declared in his Epistle to the Ephesians, becoming envious of man, was rendered an apostate from the divine law: for envy is a thing foreign to God. And as his apostasy was exposed by man, and man became the [means of] searching out his thoughts, he has set himself to this with greater and greater determination, in opposition to man, envying his life, and wishing to involve him in his own apostate power. The Word of God, however, the Maker of all things, conquering him by means of human nature, and showing him to be an apostate, has, on the contrary, put him under the power of man. For He says, "Behold, I confer upon you the power of treading upon serpents and scorpions, and upon all the power of the enemy," in order that, as he obtained dominion over man by apostasy, so again his apostasy might be deprived of power by means of man turning back again to God. Irenaeus (A.D. 180) Ante-Nicene Fathers vol.1 pg. 553
We know that "Satan himself is transformed into an angel of light" - much more into a man of light - and that at last he will "show himself to be even God," and will exhibit "great signs and wonders, insomuch that, if it were possible, he shall deceive the very elect." Tertullian (A.D. 198) Ante-Nicene Fathers vol.3 pg. 234
SEE ALSO: DEMONS, ANTICHRIST, FALL OF MAN, ATONEMENT