Upon his return, he regained the lost ground resulted from the First Council of Nicaea, established alliances with other groups such as the Meletians and expelled many opponents.
Damian was very active in fighting views that he considered heretical, including not only tritheism, but also the Chalcedonians, Pope Leo's Tome, Bishop Julian of Halicarnassus, the Agnoetae, the Meletians, the Acephali, the Gaianites (supporters of a rival to Theodosius I), Stephen of Alexandria and Paul of Beth Ukame.