 Complete the following phrase:  His followers later developed into a distinct Shia sect known as the Kaysanites. They introduced the doctrines of Occultation Ghayba and Return Raja of the Mahdi. After the death of Ibn al-Hanafiyyah, some Kaysanites believed that he had not died but was hidden in Mount Radwa and would return some day to rid the world of injustice. Most Kaysanites, however, declared his son Abu Hashim to be their Imam. He then transferred the Imamate to Muhammad ibn Ali ibn Abdallah ibn Abbas before dying. The Abbasids used this as a propaganda tool during their 