St Cyriacus was martyred in the persecution of Diocletian in 303 AD.
One of the interesting features of some of the early persecutions is that they may have been sparked by the threat to pagan religion posed by the conversion of very senior nobles, and this may have been one of those cases.
St Cyriacus was a Roman nobleman who converted to Christianity as an adult and, renouncing his material wealth, gave it away to the poor. He spent the rest of his life ministering to the slaves who worked in the Baths of Diocletian.
Under the reign of Western Roman Emperor Maximian, co-emperor with Diocletian, St Cyriacus was tortured and put to death, beheaded in 303 on the Via Salaria, where he was subsequently buried. With him were martyred his companions Largus and Smaragdus, and twenty others, including Crescentianus, Sergius, Secundus, Alban, Victorianus, Faustinus, Felix, Sylvanus, and four women: Memmia, Juliana, Cyriacides, and Donata.
Saint Cyriacus is credited with exorcizing demons from two girls. The first was Artemisia (or Artemia), the daughter of Emperor Diocletian, which resulted in both Artemisia and her mother Saint Serena converting to Christianity. The second was Jobias, the daughter of Shapur II of
He is one of the fourteen holy helpers.