Who or what is the Antichrist? It's in the Bible, 1 John 2:18 NIV. “Dear children, this is the last hour; and as you have heard that the Antichrist is coming, even now many antichrists have come. This is how we know it is the last hour.” God is here speaking to the early church. Obviously, the word 'hour' is used in a figurative sense. The same word in the original Greek is often translated as 'time', for example as in the King James translation of this same verse. God is stating that mankind is living in the 'last time', the last era, the last dispensation, the last period of Earth's history. Theologians call this time period the 'dispensation of the Church', or the 'Church age'. God is reminding the early-church brethren of a prophecy they had already heard; namely, that the Antichrist was going to come.
The original Greek word for 'antichrist' can have two meanings. It can mean 'against Christ', in the sense of someone or some power who opposes the work of Christ. Or alternatively, the word can mean 'instead of Christ', signifying a person or power who 'takes the place of Christ', or is a 'counterfeit of Christ'. In the verse we read, God informs the brethren that in addition to the coming of a special Antichrist, there were many other antichrists already in existence during the era of the early church. The Bible explains in 1 John 2:19 & 26 NIV, “They (the antichrists) went out from us, but they did not really belong to us. For if they had belonged to us, they would have remained with us… I am writing these things to you about those who are trying to lead you astray.” Thus, according to God's Word, the antichrists were counterfeit Christians who had split away from the body of true believers. They were deceivers who had not really experienced a genuine gospel conversion. They were liars who denied the Messiahship of Jesus; for the Bible declares in 1 John 2:22 NKJV, “Who is a liar but he who denies that Jesus is the Christ? He is antichrist who denies the Father and the Son.” In 2 John 1:7, NKJV, God states “For many deceivers have gone out into the world who do not confess Jesus Christ as coming in the flesh. This is a deceiver and an antichrist.” And in 1 John 4:1 NKJV, Scripture admonishes “Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world.”
The deceiving antichrists are even preaching a gospel, but it is not the true gospel. It is a 'different gospel'. The Bible warns in 2nd Corinthians 11:4 & 13-15 NIV, “For if someone comes to you and preaches a Jesus other than the Jesus we preached, or if you receive a different spirit from the one you received, or a different gospel from the one you accepted, you put up with it easily enough…For such men are false apostles, deceitful workmen, masquerading as apostles of Christ. And no wonder, for Satan himself masquerades as an angel of light. Is it not surprising, then, if his servants masquerade as servants of righteousness.” Thus, in contrast to the popular view which regards antichrists to be anti-Christian atheists and pagans, the Bible teaches that antichrists are actually false prophets and false apostles who masquerade as real Christians. Antichrists sincerely regard themselves to be genuine followers of Christ, but in reality they are empowered by the spirit of Satan, and they are opposing the work of God.
Jesus cautioned the Church about the deceptive work of these counterfeit prophets, declaring in Matthew 7:15 NAS, “Beware of the false prophets, who come to you in sheep's clothing, but inwardly are ravenous wolves.” In verses 21 thru 23, Christ describes the tragic fate to be faced by these false believers on the day of His Second Coming. Jesus warns, “Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of heaven; but he who does the will of my Father who is in heaven. Many will say to me on that day, 'Lord, Lord, did we not prophesy in your name, and in your name cast out demons, and in your name perform many miracles?' And then I will declare to them, 'I never knew you; depart from me, you who practice lawlessness.' ” Even though the false apostles claim to be Christians, even though they can perform signs and miracles, including casting out demons in the 'name of Jesus', Christ declares that he does not know them. Because of their lawlessness, their disregard for God's Holy Law, they are turned away from entering into the kingdom of heaven.
Jesus further warned that during the period leading up to his Second Coming at the end of the Church age, antichrists would verily try to impersonate him, claiming to be the returned Messiah. It's in the Bible, Matthew 24:4 & 5 NIV. “Watch out that no one deceives you. For many will come in my name, claiming, 'I am the Christ,' and will deceive many.” In the same chapter, verses 24-26 assert: “At that time, if anyone says to you, 'Look, here is the Christ!' or, 'There he is!' do not believe it. For false Christs and false prophets will appear and perform great signs and miracles to deceive even the elect—if that were possible. See, I have told you ahead of time. So, if anyone tells you, 'There he is, out in the desert,' do not go out; or 'Here he is, in the inner rooms,' do not believe it.”
Just before the day of the Second Coming of Jesus, is there going to manifest a great and final Antichrist, the antichrist who 'is to come'? Yes, it's in the Bible, 2nd Thessalonians 2:3 & 4 NIV. “Don't let any one deceive you in any way, for that day will not come until the rebellion occurs and the man of lawlessness is revealed, the man doomed to destruction. He will oppose and will exalt himself over everything that is called God or is worshiped, so that he sets himself up in God's temple, proclaiming himself to be God.” In this profound prophecy of Last Day events, the Bible says that there is going to be a rebellion, an apostasy, a great falling away from the faith. In conjunction with this apostasy, there will be a revealing of the 'Man of Lawlessness', the Antichrist, also known as the 'Man of Sin'. This grand Antichrist will set himself up in God's temple and counterfeit the ministry of Jesus.
What will happen to this Antichrist, and how will we recognize him? It's in the Bible, 2nd Thessalonians 2:8-10 NIV. “And then the Lawless One will be revealed, whom the Lord Jesus Christ will overthrow with the breath of his mouth and destroy by the splendor of his coming. The coming of the Lawless One will be in accordance with the work of Satan displayed in all kinds of counterfeit miracles, signs and wonders, and in every sort of evil that deceives those who are perishing. They perish because they refuse to love the truth and so be saved.”
The way to avoid being deceived by the coming great Antichrist and his counterfeit miracles, is to have a love of the truth. That same truth will protect us from the wiles of the other lesser antichrists. And where is the truth to be found? It's in the Bible, Psalm 119:160 Amplified Version, “The sum of your Word is truth, and every one of your righteous decrees endures forever.”