The Martyrs Agathonicus, Zoticus, Theoprepius, Acindynus, Severian, Zeno and others accepted death for Christ during the reign of the emperor Maximian (284-305).

The Martyr Agathonicus was descended from the illustrious lineage of the Hypasians, and he lived at Nicomedia. Well versed in Holy Scripture, he converted many pagans to Christ, including the most eminent member of the Senate (its "princeps" or leader). Comitus Eutolmius was sent to the Pontine (lower Black Sea) region, where he crucified the followers of the Christian Zoticus, who had refused to offer sacrifice to idols. He took Zoticus with him.

In Nicomedia, Eutolmius arrested the Martyr Agathonicus (together with the princeps), and also Theoprepius, Acindynus and Severian. After tortures, Eutolmius ordered that the martyrs be taken to Thrace for trial by the emperor.

But along the way, in the vicinity of Potama, the Martyrs Zoticus, Theoprepius and Acindynus were unable to proceed further behind the chariot of the governor because of wounds received during torture. Therefore, they were put to death. The Martyr Severian was put to death at Chalcedon, and the Martyr Agathonicus together with others was beheaded with the sword by order of the emperor, in Selymbria.

The relics of the Martyr Agathonicus were in a church named for him at Constantinople, and were seen in the year 1200 by the Russian pilgrim Anthony. And in the fourteenth century Philotheus, the archbishop of Selymbria, devoted an encomium to the Martyr Agathonicus.