أحمد بن يحيى
Ali bin al-Mu'ayyad was a fifth-generation descendant of the imam al-Hadi Yahya (d. 1239). After the demise of imam an-Nasir Muhammad Salah ad-Din in 1391, a struggle broke out between his son al-Mansur Ali and another contender, al-Mahdi Ahmad bin Yahya. Al-Mansur imprisoned his opponent in 1392, but was then challenged by Ali bin al-Mu'ayyad, who took the honorific ("laqab") name al-Hadi Ali. During his almost 40 years long imamate he was generally overshadowed by al-Mansur Ali, who was celebrated as a "mujaddid bi-sayfihi", a warlike restorer, and who died only in 1436. Nevertheless, al-Hadi Ali had a following and was counted by some as a mujaddidun. These are figures who, according to a hadith, will appear every century to restore Islam. He died in 1432, leaving ten sons, of whom al-Hasan (1401–1486) became a prominent scholar. Al-Hasan's son in turn, al-Hadi Izz ad-din, held the Zaidi imamate in 1474–1495.