Imam Ali al-Hadi (AS)

In 233 AH the caliph al-Mutawakkil brought him from Medina to Samarra, then the Abbasid capital, and kept him under surveillance there. He and his son Imam al-Askari (AS) became known together as al-‘Askariyyayn. [WikiShia] [WikiShia]

Al-Mutawakkil also had the shrine of Imam Hussain (AS) in Karbala destroyed, its land ploughed and pilgrims punished, because the grave had become a bond between the Shia and their Imams. [WikiShia]

Al-Ziyara al-Jami‘a al-Kabira, a long salutation to all the Imams that sets out Shia belief about them, is narrated from him. His students included Abd al-Azim al-Hasani. [WikiShia]

He died in Samarra in Rajab 254 AH, after twenty years and nine months there, and was buried in his house, over which the shrine now stands. [WikiShia] [WikiShia]