Theopemptus, bishop of Nicomedia, and Theonas, a sorcerer converted to Christ, are commemorated together on January 5 as martyrs of the persecution under the Emperor Diocletian. By tradition they suffered at Nicomedia in Asia Minor around the year 303, at the outset of the great persecution, with Theopemptus counted among its first victims.
Theopemptus is remembered for speaking out against idolatry and refusing the emperor's command to worship an idol of Apollo. The accounts of his passion relate a sequence of tortures that he survived: cast into a red-hot furnace, he remained unharmed, and when deprived of food and drink for twenty-two days he was preserved alive. Ascribing these wonders to magic, Diocletian summoned a renowned sorcerer named Theonas to overcome the bishop.
Theonas attempted to poison Theopemptus, by tradition first with poison concealed in a cake and then with a stronger dose, but both proved harmless. Witnessing the bishop's survival, Theonas abandoned his arts and professed faith in Christ; Theopemptus baptized him, giving him the name Synesios. The two were thereafter held together. Theopemptus was subjected to further tortures and beheaded, while Theonas, refusing to sacrifice to idols, was buried alive in a deep ditch.