Witnesses to Christ unto giving their lives
Blaise (or Blastus) and Diogen (or Diogenes) are two saints who have been venerated in Rome since antiquity and throughout the Middle Ages. Their commemoration is recorded in the Martyrologium Hieronymianum under the date of June 17.
Regarding Saint Blaise, some texts — including the Acts of the Martyr Saint Valentine — refer to a Roman Tribune named Blastus, who was condemned to death in 269 AD by Emperor Claudius Gothicus for his Christian faith. However, there is no conclusive evidence to confirm that this Blastus is the same saint remembered on this date.
As for Saint Diogen, an indirect testimony of his existence is preserved in the sepulchral epigraph of the presbyter Marea, which refers to the violation of his tomb during the siege by Vitiges in 536 AD — an event that attests to the antiquity of his memory.
Both saints were originally buried in the church of Saint John Martyr, located along the Via Salaria ad septem palumbas (near what is now Acqua Acetosa), where they were venerated, as reported by various medieval itineraries.
In the 9th century, Pope Paschal transferred their relics to the Basilica of Saint Praxedes, as documented by the marble catalogue. Additional relics are also preserved in the church of San Marcello al Corso, as confirmed by an inscription dating to the 11th–12th century.
Their memory is included in the Roman Martyrology on June 17.