What is "al-musta'li"

Abū'l-Qāsim Aḥmad al-Musta‘lī bil-Lāh (16 September 1074 – 12 December 1101, ) was the ninth Fatimid caliph, and believed by the Mustaali sect of Isma'ilism to be the nineteenth Imam.

Al-Musta‘li was made caliph by vizier al-Afdal Shahanshah and was the successor to al-Mustansir Billah. By and large, al-Musta‘li was subordinate to Malik al-Afdal. One complication with the selection of al-Musta‘li was that his older brother Nizar was considered by Nizar's supporters to be the rightful heir to the throne. This led to a power struggle within the Fatimids, and although Nizar's revolt was unsuccessful (ending with his death in prison in 1097), the break from the rules of succession caused a schism among Isma'ili Shi'i Muslims. In Seljuq-ruled Syria and Iran, the Nizari sect developed.

During al-Musta‘li's reign, the First Crusade (1099) established the Kingdom of Jerusalem, the County of Tripoli and the Principality of Antioch, which further reduced Fatimid power in Syria and Palestine. He was succeeded by his son al-Amir bi-Ahkami'l-Lah (r. 1101–1130), after whose reign the Mustaali sect again split into the Hafizi and Taiyabi; the former are extinct.