Saint Theophylact lived in Constantinople in the 8th century during the iconoclastic heresy. After the death of the iconoclast Emperor Leo IV Khazar (775-780), Emperor Constantine VI (780-797) ascended the throne. There was also a change of patriarchs: Holy Patriarch Paul (August 30), unable to manage his flock with widespread iconoclasm, voluntarily left the pulpit (784). Saint Tarasius (February 25), at that time the first royal adviser, was elected in his place. At the insistence of the new patriarch, the Seventh Ecumenical Council (787) was convened, condemning the iconoclastic heresy. These are relatively peaceful times for Orthodoxy. Monasteries began to be replenished with monks again.
Saint Theophylact, a devoted disciple of Saint Tarasius, with the blessing of the patriarch, together with Saint Michael (May 23), retired to a monastery on the Black Sea coast. The zealous ascetics received the gift of miracle-working from God through their godly labors and concentrated prayer. According to their prayers, during a severe drought, when the reapers in the field were exhausted from thirst, the empty vessel began to emit so much water that it was enough for the whole day.
After several years in the monastery, they were both consecrated to the episcopate by Patriarch Tarasius. Saint Michael was appointed Bishop of Sinada, and Saint Theophylact was appointed Bishop of Nicomedia.
As head of the Nicomedia Church, Saint Theophylact tirelessly cared for the flock entrusted to him. He built temples, hospitals, hospices, generously distributed alms, took care of orphans, widows and the sick, and took care of lepers himself, not disdaining to wash their wounds.
When the iconoclast Leo V the Armenian (813-820) took the imperial throne, the terrible heresy flared up with renewed vigor.
The iconoclast emperor could not be influenced by the successor of the holy Patriarch Tarasius, Saint Nikephoros (806-815; commemorated on June 2), who, together with the bishops, tried in vain to convince the ruler not to violate church peace. Saint Theophylact, who was present at the negotiations between the emperor and the patriarch, denounced the heretics and predicted the imminent death of Leo the Armenian. For his bold prophecy, the saint was sent into exile to the fortress of Stroville (in Asia Minor). Here he languished for thirty years until his death, which followed around 845.
After the restoration of icon veneration in 847, during the reign of Empress Saint Theodora (842-855; + 867, February 11) and her son Michael, the holy relics of Bishop Theophylact were transferred to Nicomedia.