Martyrdom
The accounts agree that Demetrius was imprisoned after the emperor learned of his Christian faith and the conversions he had brought about. During pagan games celebrated in the city, a young Christian named Nestor sought Demetrius's blessing and then defeated a champion described as a Germanic giant named Lyaeus (Lyaios) in single combat.
In retaliation, the emperor ordered both men killed: by tradition Nestor was beheaded outside the city, and Demetrius was run through with spears in his underground prison at dawn on October 26, around the year 306. One account also relates that his servant Lupus was later beheaded after performing miracles using Demetrius's blood-stained tunic and ring.
Christians secretly buried his body, and a church was afterward constructed over his grave.