Kaysan converted to Islam after the Muslim conquest of Persia and became a mawlā affiliated with the Urayna clan of the Arab tribe of Bajila.
He ultimately became a leader of the mawālī faction in the pro-Alid movement of al-Mukhtar al-Thaqafi (685–687 CE), serving as the head of the latter's personal guard.
[3] He was among the handful of al-Mukhtar's loyalists who secured the support of the prominent leader Ibrahim ibn al-Ashtar for the pro-Alid movement.
[3] His fate is not precisely known but he may have died during the Battle of Madhar, in which he again commanded the mawalī of al-Mukhtar's army, in mid-686 since there is no post-battle mention of him in the sources.
He is alleged to have asserted that Ali had designated Muhammad ibn al-Hanafiyyah as his successor as Imam, and that Hasan and Husayn were usurpers.