Ubaydallah ibn Abdallah ibn Tahir was the last major Tahirid to hold high office in what dynasty?
Tahirid dynasty The Tahirid dynasty (Persian: طاهریان‎ ‎ , "Tâhereyân") was a dynasty, of Persian dihqan origin, that governed the Abbasid province of Khorasan from 821 to 873 and the city of Baghdad from 820 until 891. The dynasty was founded by Tahir ibn Husayn, a leading general in the service of the Abbasid caliph al-Ma'mun. Their capital in Khorasan was initially located at Merv but was later moved to Nishapur. The Tahirids enjoyed a high degree of autonomy in their governance of Khorasan, but they remained subject to the Abbasid caliphate and were not independent rulers.
Al-Mu'tadid Abu'l-Abbas Ahmad ibn Talha al-Muwaffaq (854 or 861 – 5 April 902), better known by his regnal name al-Mu'tadid bi-llah (Arabic: المعتضد بالله‎ ‎ , "Seeking Support in God" ) was the Abbasid Caliph in Baghdad from 892 until his death in 902.