From Wikipedia: End of time beliefs in Shia Islamic thought
End of time beliefs in Shia Islamic thought are based on Quranic references, instruction from the Prophet Muhammad and his progeny Ahl al-Bayt. Several variants of one theory exist in Shia eschatology, yet they all revolve around the messianic figure, Imam Mahdi also known as "Imam az-Zaman" meaning the Leader of Our Time, who is considered by Twelver Shias as the 12th appointed successor of Prophet Muhammad. He is Mohammad (Al-Mahdi), son of Hasan (Al-'Askari), son of Ali (Al-Hadi), son of Mohammad (Al-Jawad), son of Ali (Al-Rida), son of Musa (Al-Kathem), son of Jafar (As-Sadeq), son of Mohammad (Al-Baqer), son of Ali (Zainul-abideen), son of Hussein (Ash-Shahid), son of Ali (Amirul Mu'mineen) husband of Prophet Mohammad's daughter, Fatima.
Even though during the days of the Shia Imams (more than a thousand years ago), Iran was still Persian and non-Muslim; it is mentioned in Shia traditions (which were narrated from the Shia Imams of Ahlul Bayt), that people from Iran (often referred to people from the East, also) will pave the way to Al-Mahdi's appearance, and after his return, the Iranians will side with him and fight his enemies. Prior to Imam Mahdi's return, the Iranian army, whose leader will be a man called in Shia traditions as: Al-Khorasani (in reference to Khorasan, a region in Iran), will be sent to Kufa to fight Sufyani's army, which will be sent from Syria to slaughter the Shia of Iraq.
It is important to draw a line between the "signs" that correlate to Imam Mahdi's return, and the "signs" that occur prior to Judgment Day. According to Shia beliefs, there are many signs that will occur before Imam Mahdi's appearance, but only 5 of those are guaranteed to occur, while the rest are uncertain to people, depending on God's will. If He wishes them to occur or not, it is what He decides. God has hidden His will with regards to those uncertain signs for the well-being of mankind, for He is the most knowledgeable to what serves mankind good and what harms it. This what is known in Shia beliefs as "Badaa" (البداء
.
The five signs that are imminent are the following:
The appearance of a person by the name of "Sufyani" (claims to be Muslim, though he 'carries a cross', though he is a descendant of the disintegrated Ummayyad dynasty whose scattered descendants may have been in the Levant and Spain or Morocco over the last 12 centuries) will lead forces from Syria across Iraq to Arabia to defeat the Mahdi's forces along with his Allies
The cracking of the earth to abolish Sufyani's forces as previously mentioned.
The appearance of al-Yamani, the ruler of Yemen, who will be a guide to people to the right path before Imam Mahdi's appearance
The voice of Gabriel, the angel, from the sky that calls out people to support Imam Mahdi because he is sent by God.
It is mentioned in Shia traditions, that Imam Mahdi's army will destroy the Jewish state, which was predicted by Islam more than 1400 years ago, that was established in the Middle East. After that, Imam Mahdi will fight al-Sufyani and eventually destroy him and his army too. It is after those events that the Jews gather once again under the Dajjal ,the anti-Christ, as Christians call him, the deceiver, who will try to influence people once again to side with him against Imam Mahdi's wordly revolution.
The Shia End of Time theory also states that the coming of Jesus, will coincide with the return of the Mahdi. Shias believe that Jesus and the Mahdi will work together to bring about peace and justice on earth between all peoples of faith. This is the general theme accepted among Shia theologians.
The events that occur in the final moments of humanity will mainly revolve around Dajjal and his ability to woo humanity to a new world religion, one that is not divinely issued. The idea of a Mahdi returning to help humanity against the "Great Deception" is also mentioned in Sunni traditions, but is specifically outlined as Muhammad al-Mahdi in Shia sources. There are many sources that have prophecies regarding the last days, with only some that are accepted as repeated in different sources by different people. A majority of Shia scholars[who?] agree on the following detail of events that will occur in the final days:[citation needed]
The Dajjal (Al Masih Al Dajjal - The Antichrist) will claim to be the savior of humanity and people of all faiths will unite under his religion
There will be mass killings of Shias in Iraq (around the Euphrates), and there will be prices put on their hands, even if they are not criminals
The Mahdi will reappear and make a speech at the Kaaba and will gather an army of 313 generals and thousands of followers to defeat the Sufyani
The Mahdi will re-establish the true Islam and the world will find peace and tranquility
There will be a period of rule by the Mahdi
The resurrection of men and women will begin as the Day of Judgement will commence