Shias believe that Allah continues to appoint successors to Ali – and they call this line of succession the Imamate. These successor Imams are given divine insight so that they can interpret the Quran without error. Today, there are three major groups of Shias who disagree about who succeeded Ali: the Twelvers (85% of Shias), the Zaydis in Yemen, and the Ismailis in Pakistan and India.
Surprisingly, the Shias changed the Sunni Confession of Faith (the Shahada): “There is no god but Allah, and Muhammad is the Prophet (or messenger) of Allah”. They add “and Ali is the friend (or holy man) (wali) of Allah.” Given that Ali and his sons suffered much, it is not surprising that Shia Islam stresses suffering and martyrdom.
During the Ashura Festival, which commemorates the martyrdom of Husain, men and boys beat themselves until their bodies run with blood.Shias believe that the final Imam (Mahdi) will return before the Day of Judgement and be joined by Isa (Jesus).
The Mahdi will lead Muslims in a final war against Dajjal, the false Messiah, and Isa will kill him. Then the Mahdi and Isa, they believe, will rid the world of evil and unite all in submission to Allah.