Who is Al-Mahdi?

Most major (Abrahamic) faiths have the belief that eventually peace and justice will spread across the world by the means of an elevated individual. Followers of Islam believe the name of that person is Mahdi (A.S) and is from the bloodline of the prophet Muhammad (S). He will one day appear together with prophet Jesus (A.S) and establish peace and justice in the world after it has been overtaken by oppression and injustice.