The promised Mahdi

He is the only child of Imam Askari (as), the eleventh Imam of the Shiites. The Imam of the time of Hazrat Mahdi (pbuh) was born at the dawn of mid-Sha'ban 255 AH in Samarra and after five years of living under the care of his noble parents Narjes Khatoon, .
At the age of five, they took over the leadership of the Shiites. That noble man will rule over the whole earth after the end of the time of absence with the formation of the world government of justice.
The shrine of Al-Mahdi is a cry that has come from God to reach the cry of the people. In his day, everyone achieves unparalleled blessings in prosperity and comfort, even cattle multiply and live happily with other animals, plants grow abundantly and streams abound, and treasures, burials, and other mines of the earth are extracted. The fire of sedition and riots is extinguished and war, ambush and looting are eliminated. It will not remain a ruin in the world, unless Mahdi builds it.
Al-Mahdi's justice is so pervasive that it even infiltrates homes and affects the private relationships of family members, something that no legal system can do. Imam Sadegh (as) says: "By (God) the Mahdi will bring his justice to the last corners of people's homes, just as cold and heat enter our homes."

Imam Reza (pbuh) in describing the features of the face and moral virtues and outstanding features of the Imam says: "Ghaem Al-Muhammad (pbuh) is surrounded by auras of light on his beautiful face. In terms of physical characteristics, he is the most similar to the Messenger of God (PBUH). His special sign is that although he is very old, he has a youthful appearance; To the extent that every viewer imagines him to be forty years old or younger. "Another sign of him is that he will never show the signs of aging on his face until he dies, despite the passage of time."
One of the most important things that Imam Hassan Askari (as) did during this period was to introduce Imam Mahdi (as) to the Shiite elders so that they would not have any disagreements on the issue of Imamate in the future.
To be safe from the conspiracy of the enemies by the will of God
They live among the people but in secret.

Minor Absence: After the martyrdom of Imam Hassan Askari (as) in 260 AH, the period of minor occultation began and continued until 329 AH. During this period, Hazrat Mahdi (pbuh) continued the affairs of the people through four deputies.
The period of Cobra's absence: This period began in 329 AH and will continue until God deems it expedient.
After his reappearance, the Imam of the Age (pbuh) will form a single world government based on the rules of Islam, in the shadow of which the whole world will be filled with justice.