About Mahdi
The Mahdi is a messianic figure in Islamic belief. He is comparable to the Christian concept of the Second Coming of Jesus Christ, the Jewish concept of Mashiach ben David and the Zoroastrian concept of the Saoshyant. The Mahdi is said to be a descendant of Muhammad and is believed to appear at the End of Times, shortly before Jesus returns, to rid the world of evil and injustice.
Biography source:
Wikipedia
