He lived during the reign of Emperor Leo the Armenian, who resumed the harsh persecution of the defenders of icon veneration. His ascetic feats as a monastic earned him the gift of miracle-working. He also went on record as a fearless defender of the true faith who ended his life in exile for daring to oppose the iconoclastic emperor Leo the Armenian.
After the Seventh Ecumenical Council condemned the iconoclastic heresy in 787, peace installed itself in church life. The monasteries and monks who did not stop icon veneration ended, and gradually, the flow of people to monasteries resumed. Saint Theophylactus went to a monastery on the Black Sea Coast and engaged in God-pleasing works and ardent prayer. For his righteousness and piety, he acquired the gift of wonderworking by the grace of the Holy Spirit. During a severe drought, when the lack of water weakened the strengths of the working monks, he prayed to God, and a vessel was filled with enough water to last them through the day.
When the Patriarch of Constantinople ordained him as bishop of Nicomedia, he became a loving shepherd to his flock and spared no effort to ease the plight of the sick and needy. He gave alms, build hostels for indigent wanderers, took care of orphans, and attended to the needs of people with leprosy, not fearing to wash their wounds when needed.
The iconoclast heresy resumed after the ascent to the throne of Emperor Leo the Armenian. The patriarch of the church, Saint Nikēphóros tried in vain to convince the emperor to reconsider and not destroy peace in the church. Saint Theophylactus was present at these talks. Seeing that persuasion was not working, he stood before the emperor, condemned the heresy and predicted his speedy death. For his boldness, the emperor sent him to exile, where he spent 30 years, dying around 845. When Empress Theodora ended iconoclasm, his relics were returned to Constantinople.
