The document compiles a Martyrologium detailing the lives, martyrdoms, and miracles of numerous saints and martyrs throughout the liturgical year, often specifying their feast days. It recounts the suffering and devotion of early Christian figures, popes, bishops, virgins, and monks, highlighting their steadfast faith during periods of intense Roman persecution under emperors such as Diocletian, Maximian, Nero, Decius, Valerian, Gallienus, and Julian. Descriptions include various forms of torture and execution, the veneration of their remains, and the translation of relics. The text also records significant Church events like the Circumcision of Christ and Epiphany, the dedication of churches, and the spread of Christianity through miracles and preaching. It references key historical figures such as Pope Gregory the Great, Pope Innocent I, Pope Celestine, and the historian Egesippus, and mentions specific ecclesiastical practices and the establishment of rules for sacred mysteries.