What do you know and what do you believe about this person whom some people claimed that Prophet Muhammad prophesied as Mahdi and this event called Dajjal Fitnah. I’m not sure but I think these are unfounded claims as far as the Qur’an is concerned. I don’t know but some people relate these things to what is happening in Syria.
There are several authentic hadeeths, reported in Al-Bukhaari and Muslim’s compilations and narrated by Al-Khudri, Ibn Umar and others, which mention Al-Maseeh Ad-Dajjaal (the luring messiah). In these hadeeths, the Prophet (PBUH) forewarns Muslims of the coming of the Anti-Christ, a man who will possess great powers, even power to resurrect people from the dead, and succeed in luring most people away from true faith to follow him instead. He will claim to be God. The Prophet (PBUH) said that the Dajjaal Fitna (test of faith) is the greatest and that every prophet had forewarned his people against it.
While the Quran does not mention Ad-Dajjaal, there is no reason to doubt the story. It would be a different matter if the Quran has contradicted the story. One authentic hadeeth I know of is reported by Al-Bukhaari and narrated by `Aa’isha, may God have been pleased with her, in which she relates that the Prophet (PBUH) used to say in his supplication during prayer, “O God, I seek refuge in You from the trying times of the Luring Messiah.”
Several authentic hadeeths also mention the coming of the Anti-Christ as one of several grand signs of the approach of the Hour (the Day of Judgment). Most of the signs mentioned in those hadeeths are also mentioned in the Quran, such as the second coming of Jesus Christ, the release of Gog and Magog, and the animal which will preach to people. Thus, there is no cause to deny the story about the Anti-Christ while the other, equally spectacular stories are confirmed by the Quran.
There is no evidence that the war in Syria has anything to do with the Anti-Christ.
As for Al-Mahdi (the guided one), the hadeeths about him are far less authentic. Neither Al-Bukhaari nor Muslim have reported any hadeeth about him, to the best of my knowledge. Whether he will exist has no bearing on your or my faith, since we already have all we need to be true believers: the holy Quran and the authentic Sunna.