 The regency moved quickly to end Byzantine Iconoclasm , which had dominated Byzantine religious and political life for over a century with deleterious effects . In early 843 , an assembly of selected officials and clerics convened in the house of Theoktistos . The synod repudiated iconoclasm , re @-@ affirmed the decisions of the 787 Second Council of Nicaea , and deposed the pro @-@ iconoclast patriarch John the Grammarian . In his stead was elected Methodios I , who had been imprisoned by Theophilos for his iconophile beliefs . This event is commemorated as the " Triumph of Orthodoxy " by the Eastern Orthodox Church ever since . Theoktistos played a major role in these events . He is credited by almost all sources — Theophanes Continuatus , Genesios , John Skylitzes , and Zonaras — as a driving force behind the restoration of the icons , and particularly behind the deposition of John the Grammarian . He is commemorated as a saint by the Orthodox Church on 20 October . 
