In 445 he summoned a synod of Syrian bishops which confirmed the deposition of Athanasius of Perrha. In 447 he consecrated Irenaeus to the see of Tyre (Theodoret, Epistle 110); but emperor Theodosius II, commanded that the appointment should be annulled on the grounds that Irenaeus was both a digamus and a supporter of Nestorianism. He defended Ibas, bishop of Edessa, against charges of promulgating Nestorian doctrines, and summoned a council at Antioch (448) which decided in favor of Ibas and deposed his accusers. Domnus's sentence, though revoked by Flavian, Patriarch of Constantinople, was confirmed by three episcopal commissioners to whom he and the emperor Theodosius had committed the matter. As a result, he was deposed at the Robber Council of Ephesus on August 8, 449. Cowed by the authoritarian spirit of Dioscorus, and unnerved by the violence of Barsumas and his monks, Domnus revoked his former condemnation of Eutyches, and voted for the condemnation of Flavian, but in vain. He was the only bishop then deposed and banished who was not reinstated after the Council of Chalcedon. At that council Maximus II, his successor in the see of Antioch, obtained permission to assign Domnus a pension from the revenues of the church, and on his recall from exile Domnus returned to the monastic home of his youth, ending his days in the Laura of St. Euthymius, where in 452, according to Theophanes, he afforded a refuge to Juvenal of Jerusalem when he was driven from his see (Theophanes, p. 92).