[2] His father, Abd al-Malik, had made a fortune as an oil trader (whence his sobriquet al-Zayyāt) in Baghdad at the time of al-Ma'mun (r. 813–833), and became involved in the lucrative government contracts for tents, ceremonial parasols (al-mushammas), and riding equipment.
[12] In the process, Ibn al-Zayyat became notorious for the severity and cruelty with which he treated the prisoners, torturing them with a device of his own invention, the tannur ("oven"), a kind of iron maiden.
[15] Like al-Ma'mun, he was rumoured to be a zindīq, which normally meant "Manichaean", but was also used a shorthand by orthodox Sunni writers to denounce those with heterodox (pro-Shi'ite) beliefs.
[17][18] Unbeknownst to Ibn al-Zayyat and the others, the new Caliph was resolved to destroy the coterie of his father's officials that controlled the state, and furthermore harboured a deep grudge against the vizier for the way he had been mistreated by him in the past.
[19] According to al-Tabari, when al-Wathiq had grown angry and suspicious at his brother, al-Mutawakkil had visited the vizier in hopes of persuading him to intercede with the Caliph.
Not only that, but when the dejected prince left, Ibn al-Zayyat wrote to the Caliph to complain about his appearance, noting that he was dressed in effeminate fashion, and that his hair was too long.
After a few days, he was put in fetters and tortured by being kept from sleeping, while another story—frequently retold by later authors as a morality tale—claimed that he was placed inside the tannur, the same device that he had devised.
[24] These events marked the end of al-Mu'tasim's "old guard", and the full assumption of power by al-Mutawakkil, who reoriented Abbasid policy towards a traditionalist, orthodox Sunni position.