حسن الصباح
Anushirvan died in 1059 and was succeeded by his cousin Keikavus, the celebrated author of the Qabus nama, a major work of Persian literature. Keikavus died in 1087, and was succeeded by his son Gilanshah. Gilanshah's reign, was, however, short; in 1090, the Nizari Ismaili state under Hassan-i Sabbah invaded and conquered his domains, which ended Ziyarid rule in Tabaristan.