Al-Masih ad-Dajjal (Arabic: المسيح الدجّال Al-Masīḥ ad-Dajjāl, "the false messiah, liar, the deceiver") is an evil figure in Islamic eschatology. He is to appear, pretending to be al-Masih (i.e. the Messiah), before Youm al-Qiyamah (the Day of Resurrection).
Dajjal is the last leader of falsehood, will come before the reappearance of Imam Al-Mahdi (AS). He will be killed by the last leader of righteous, Imam Al-Mahdi (A.S.). Dajjal is one of the definite signs of the reappearance of Imam Al Mahdi (A.S.). Dajjal will lead an army of the enemies of Ahlulbayt and fight against Imam Al-Mahdi (A.S.) and he will be defeated. (Al Amali by Al Toosi, Page 459). It is mentioned in Kamaal Ad-Din Page 336 from Imam Jafar As-Sadiq (A.S.) that Imam Al-Mahdi (A.S.) will kill Dajjal. Unfortunately, we read narrations in some Sunni books, which are taken from Non-Muslims and it go against the Truth. For example, the narration in Sahih Muslim which is called Hadeeth Al-Jassasa Volume 8 Page 204 & Hadeeth in Sahih Al Bukhari about Ibn Sayyad who is according to the narration of Bukhari the Dajjal. Ibn Hajar Al-Asqalani in Fath Al-Bari Volume 13 Page 276 confirmed his opinion that Dajjal is still alive. We don’t have in our authentic narrations the exact date when Dajjal was born and in fact we don't need it, but we only need to know that Dajjal is a devil satanic leader and he will lead his followers to the hellfire, and he will fight against Imam Al-Mahdi (A.S.) and he will be killed by Him. (Al Amali by Al-Toosi Page 527, Al- Bihar Volume 76 Page 74, Al-Waafi Volume 26 Page 186).
I did not find any authentic Hadeeth in Shia books of Hadeeth suggesting that most of Dajjal's followers will be women. It is narrated in many Sunni books e.g. Musnad Ahmad Ibn Hanbal from Abdullah Ibn Omar.
Dajjal or Antichrist will be before the reappearance of Imam Al-Mahdi (AS) and he will be killed by Imam Al-Mahdi(AS) or by Prophet Easa (Jesus) by order of the Imam Al-Mahdi (AS).
Narrations describe the Dajjal as a male and refer to him with a male pronoun. God knows best.
When Imam Al-Mahdi (peace be upon him) appears, he will be accompanied by a set of cosmic signs known to the whole world, including the rising of the sun from the west, and the huge sound from the sky. If will be appeared to the public and he will say: I am the Mahdi from the family of Muhammad (peace be upon them), because with the emergence of these two great signs, it is impossible for the impersonators to look like his personality. Mam Al-Mahdi (AS) is supported by the divine support from Allah, and he will have the ability to practically eliminate his opponents in the East and West.
It will be obvious when the Mahdi comes because he will be accompanied by cosmic signs that will make clear that it is him (for instance, a call from the heavens, the arrival of Jesus with him). His arrival will also be apparent for all people and not confined to one group or region. (You can read more about the signs on this website.)
This is apart from the signs that all the Imams bore, such as comprehensive knowledge, knowledge of all languages, knowledge of all aspects of the religion, the ability to perform karamat, etc. Failing one of these things (for instance, not being able to understand a certain language or answer a question accurately) means he is not the Mahdi.
Anyone who does not have these signs is not the Mahdi.
In my understanding of the texts, when the Mahdi arrives, the question will not be whether he is the Mahdi or is a fake. It will be obvious that he is someone different from everyone else with a global role. The question will be whether people choose to follow him or not, as some people will not like what he stands for.
1. The definite signs of the Day of Judgement did not happen yet.
2. Dajjal is not apparent yet.
In the past few decades, some Islamic scholars have put forward the view that Dajjal is metaphorical for an evil system, such as capitalism. Others hold to the literal view in hadith that Dajjal is a one-eyed person who will arise at the end of time, have many followers, cause suffering and harm, deceive people into following him, and ultimately be defeated by the Mahdi (A). (In that, the Mahdi will be supported by Jesus (A))
It is often difficult to understand future prophecies until they happen. Certainly, many prophecies about the Dajjal would have seemed fanciful in the past. For instance, there is mention of the Dajjal having a smoky chariot that crosses great distances at great speed. However, these days, this sounds normal to us. 50 years ago, the idea that, in the end times, the believer in the east will see the believer in the west was farfetched, and yet today we can do it with mobile phones.
When it is time for the reappearance of the Mahdi (A), it will be clear. Of course, in the meantime, it is good to be cautious of things that have a Dajjal-like aspect - in particular, deceiving people and causing suffering - whether or not they are individual leaders or intangible things such as ideologies.
There are a lot of views in narrations about what Gog and Magog are. Some identify specific peoples. Some refer to them being something other than Bani Adam (i.e. not humans). Some attribute peculiar and non-human traits ot them. They are also discussed in the Jewish and Christian traditions and they also have various ideas about who they are. Some people may have been tempted to draw parallels between Gog and Magog and twentieth-century powers such as the US and the USSR; however, given that the international situation is always changing, it seems that this is unlikely. In any case, this doesn't match the Qur'anic view of them existing in ancient times and having a wall built between them (18:94-95). So, basically, this is an issue which there are many viewpoints about. For more information you can look at tafsir works on the verses of the Qur'an pertaining to Gog and Magog.
Dajjal is an evil person and he will never convince but only evil people like him. Believers know that he is a liar.