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Al-Muwaffaq was the father of al-Mu'tadid, who ruled as the Abbasid caliph from 892 to 902 CE. Al-Muwaffaq played a significant role in the Abbasid dynasty, serving as regent for his brother al-Mu'tamid and later assuming the title of caliph himself. He was known for his military prowess and his efforts to restore order and stability to the Abbasid Empire.