Twelver Shia, or Imamiyyah, is the Largest branch of Shia Islam, distinguished by the belief in a Line of twelve Imams who are spiritual and Political successors to the Prophet Muhammad. This tradition emphasizes the infallibility and Divine guidance of the Imams, with the Twelfth Imam, Muhammad al-Mahdi, in occultation and awaited as the Mahdi who will Bring justice to the world.