حسن الصباح
On the other hand, the Ismaili da‘wah ("missionary institution") sent missionaries ("du‘āt", sg. "dā‘ī") during the Fatimid Caliphate to Persia. When the Ismailis divided into two sects, Nizaris established their base in northern Persia. Hassan-i Sabbah conquered fortresses and captured Alamut in 1090. Nizaris used this fortress until the Mongols finally seized and destroyed it in 1256.