Arwa al-Sulayhi
The Musta'li consider their imam and Dais as infallible and sinless, and divinely chosen perpetuators of the true form of Islam. Their Dais are keeping the tradition which was instituted by Arwa al-Sulayhi, wife of the Fatimid Da'i of Yemen, who was instructed and prepared by al-Mustansir and the subsequent Imams for the second period of Occultation. However, in the Musta'li branch, the Dai came to have a similar but more important task. The term Da'i al-Mutlaq () literally means "the absolute or unrestricted missionary". This da'i was the only source of the Imām's knowledge after the occultation of al-Qasim in Musta'li thought.