Ustadh Sis

Ustadh Sis, also spelled Ustad Sis or Ostad Sis, was a Persian heresiarch and anti-Abbasid rebel leader active in the mid eighth century. He is speculated to have once been governor of Khorasan and possibly the father of Marajil, the Iranian mother of the caliph al-Mamun, which would make him al-Mamun's maternal grandfather. Based in the eastern fringe of Khorasan, he claimed to be a prophet of God and gained followers among the local villagers, many of them former followers of Behafarid whose own revolt the Abbasid commander Abu Muslim had already crushed militarily.