Imam Zaman

Imam Zaman (born Muhammad ibn Al-Hasan al-Mahdi, also known as Mansur ibn Muhammad) was the last of the Twelve Imams, a line of holy figures in Shia Islam. He was the son of Imam al-Askari. 
After falling from power, Imam Zaman went into hiding, established the Brethren of Purity, through which the line of Imams could continue. After going into hiding, he adopted the public identity of Mansur ibn Muhammad, and rose to become a wealthy merchant under the Sunni Caliphate. As Imam al-Ikhwan (leader of the Brethren), he was succeeded by Imam Janshan. 
Shia Islamic belief held that Imam Zaman vanished from the Earth through divine power, in an event known as the Occultation, only to return later to re-establish divine law. Staying true to this belief, Imam Zaman designed the Brethren of Purity to carry on the Imam lineage until the restoration of the Shia Imamate.