The term «antichrist» only appears a total of four times, all in I John (2:18, 2:22, 4:3) and in II John 7. It refers to several «antichrists», such as those who do not believe in Jesus; John 4:3 says: «And every spirit that confesses not that Jesus Christ is come in the flesh is not of God: and this is the spirit of antichrist, whereof ye have heard that it should come, and even now is already in the world».
Matthew 24:24 says: «For false messiahs and false prophets will appear and show great signs and wonders to deceive, if possible, even the elect».
Things change when we get to the Book of Revelation, with the appearance of the beasts and the number 666, though neither of which is directly related to the Antichrist.
It was not until 950 AD that details were written about the Antichrist. Queen Gerberga of France asked the monk Adso of Montier en Der to do so because the Bible did not really offer much information about this figure; this monk’s writings were based on people’s perceptions; the story would be structured around the idea that it would be like the second coming of Christ, for everyone to follow. However, the Antichrist would persecute Christians for three and a half years. Until the real Jesus would return and banish him.
Later Joachim of Fiore and the father of Protestantism, Martin Luther, added other visions to the concept of the Antichrist. The whole concept evolved to become a concept that represents something against Christianity, rather than an evil character. However, around 1900, thanks to German philosopher Friedrich Nietzsche, things changed; in 1895, Nietzsche published a book called «The Antichrist» bringing the name back to the mainstream. In the 1970s, Christians believed that the Antichrist was an individual.
Christ is a prophet in Islam, so there is also a figure of the Antichrist. The name of the false Messiah is Al-Masih ad-Dajjal, also known as the Dajjal; this evil figure does not appear in the Qur’an, it does in the Hadith.
Several characters have been considered as the Antichrist…Nero, Napoleon, Ronald Reagan, Obama, most of the Popes, The Beatles, etc.
And finally, we have that Revelation 13:18 attributes a number to the beast. «This requires wisdom. Let the discerning person calculate the number of the beast, for it is the number of a man. That number is 666«; the number is related to the Roman Empire, and is essentially a Jewish numerical code that translates as Nero; the number was derived using the Hebrew numerology of gematria (a Jewish form of numerology that assigns values to letters). «Hexakosioihexekontahexaphobia» is the fear of the number 666.