The famous nickname of the Imam (As) are: Mahdi , Qa im , Khalaf al-Salih , Baqiyatullah , Mansur , Sahib al-Amr , Wali al-Asr , and Sahib al-Zaman . The most famous nickname is Mahdi . Each one of these nickname has one or more reason behind them. for instance, the Imam is called Mahdi because he has been guided with the truth. He is called Qa im because he will rise with the truth. He is called Muntazar because the believers are waiting for his return. He is called Hujjah because he will divine argument against his creation.