In this paper, I explore the case of Ghazan Khan’s conversion to Islam in 1295 Mongol-ruled Iran (the Ilkhanate, 1260-1335) and the Islamic policies he implemented, which included the destruction of Buddhist shrines that were used for the worship of images of the Chinggisid ancestors. Ghazan’s conversion ended forty some years of Buddhist effloresce across Iran under Mongol auspices. Concerned with his lack of biological seniority, Ghazan’s conversion to Islam served not merely to align him with the Muslim majority, but as the installation of a “new” (ritually effective) dynastic cult that enabled him to consolidate, instrumentalize, and control access to the religious field. Combined with purging his senior cousins, conversion allowed Ghazan to monopolize charismatic resources, addressing his problem of Chinggisid under-sacralization. The destruction of Buddhist shrines was, therefore, both an iconoclastic act of conversion and a means of eradicating the access of his competition to immanent ritual power and thus, to establishing Heaven’s favor, I compare Ghazan’s efforts to Qubilai Qa’an’s adoption of Buddhism in Mongol-ruled, Yuan China to show how Chinggisids used world religions to stifle dynastic competition.