Saints Marcellinus and Peter
Saint Peter was an exorcist from Rome arrested during the Diocletian persecution. While in jail, he converted Arthemius, his jailer, and the jailer's wife and daughter. He took them to Marcellinus, a prominent priest of the city, who baptised them. All were condemned by the judge Serenus (or Severus).
The two saints were tortured, and taken to woods outside the city where they were forced to dig their own graves and then beheaded. The intent was that the Christian community would not be able to recover and venerate the bodies. But they were not forgotten. The executioner eventually converted, and led pious Christians to the bodies. And he told the martyrs' story to a young boy who became Pope St. Damasus [AD 304 - 384]. As Pope, St. Damasus had details of their martyrdom inscribed in an epitaph on their tomb. The Emperor Constantine I [AD 306 - 337] raised a basilica in their honour over their tombs, and there buried his own mother, St. Helen. During the reign of Charlemagne [AD 747 - 814] their fame spread and they were venerated throughout Italy and Gaul.
They are still remembered in the traditional Mass, together with other great martyrs of the early Church:
Nobis quoque peccatoribus famulis tuis, de multitudine miserationum tuarum sperantibus, partem aliquam, et societatem donare digneris, cum tuis sanctis Apostolis et Martyribus: cum Joanne, Stephano, Matthia, Barnaba, Ignatio, Alexandro, Marcellino, Petro, Felicitate, Perpetua, Agatha, Lucia, Agnete, Caecilia, Anastasia, et omnibus Sanctis tuis: intra quorum nos consortium, non aestimator meriti sed veniae, quaesumus, largitor admitte. Per Christum Dominum nostrum.
To us also, sinners, yet Thy servants, trusting in the greatness of Thy mercy, deign to grant some part and fellowship with Thy holy apostles and martyrs: with John, Stephen, Matthias, Barnabas, Ignatius, Alexander, Marcellinus, Peter, Felicitas, Perpetua, Agatha, Lucy, Agnes, Cecilia, Anastasia, and all Thy saints; into whose company we implore Thee to admit us, not weighing our merits, but freely granting us pardon. Through Christ our Lord.
May their memory be eternal and their reward be great.
(Sources include 1, 2, 3, 4)
Other martyrs are also remembered today. Saint Erasmus, a bishop of Syria, was killed about the same time and became widely revered as one of the Fourteen Holy Helpers. In an earlier persecution under Marcus Aurelius in AD 177, the Martyrs of Lyons and Vienne (Saint Pothinus, Saint Sanctus, Saint Marturus, Saint Attalus, and Saint Blandina, and others whose names are remembered by God) were falsely accused of cannibalism and other abominations, and brutalized and murdered in the arena. May they rest in peace and arise in glory.