Imam Nizar was born on the 10th of Rabi-el-Awwal, 437AH, 1045AD, in Cairo. He would succeed his father as the 19th Imam of the Ismailis at the age of 51 years.

During his reign, political unrest amidst a massive earthquake contributed to much of the insecurity and economic instability throughout the Fatimid territory. Notable personalities who lived during this Imam's rule include among others Hassan bin Sabbah, Nasir Khusraw, and Omar Khayyam. Pir Muhammed Shah, more commonly known as Pir Satgur Noor, was one of the Hujjatal Pirs at this time in the lineage of pirs. At the death of Imam Mustansir Billah, a split took place among the Ismailis, with the seceders, who would come to be known as the Bohras, following Caliph Mustali.

Imam Mustansir Billah was born on the 17th of Jama'di-el Thani, 420 AH, 1029AD, in Cairo. He would become the eighth Fatimid Caliph at the early age of seven years, and reign as Imam and Caliph for a period of more than 60 years.