What is "karramiyya"

Karramiyya is a sect in Islam which flourished in the central and eastern parts of the Islamic worlds, and especially in the Iranian regions, from the 9th century until the Mongol invasions in 13th century. The sect was founded by Abū ʿAbd Allāh Muḥammad b. Karrām (d. 896) who was a popular preacher in Khurasan in the 9th century.