[2] Al-Muayyad's real name was Hibatullah ibn Musa, born in the town of Shiraz, capital of the Fars province (then Persia, now in modern-day Iran), in the year 1000 CE.
His father, Musa ibn Dawud, served under the Fatimid Caliph-Imam al-Hakim bi Amr Allah as the Chief Missionary of the province of Fars, where the Isma'ili mission was active.
Al-Mu'ayyad was appointed to the Diwan al-insha' (secretariat) in 440 AH / 1048 AD on a monthly salary of 1000 dinars and wrote the religious sermons (al-Majalis) for al-Yazuri (as-Sira 89–90).
[3] Al-Muayyad (Hibatullah) gradually worked his way up the hierarchy of the da‘wa and was eventually appointed Chief Missionary under the Caliph-Imam al-Mustansir Billah.
He was appointed the head of the Academy of Science (Dar al-'Iim, originally been founded by the Caliph al-Hakim in Cairo), which was also the headquarters of the Da'wa and became the residence of al-Mu'ayyad.