St Castorius is the patron saint of sculptors and his feast day is November 8th. Castorius, Claudius, Nicostratus, and Symphorian are called "the four crowned martyrs" who were tortured and executed in Pannonia, Hungary during the reign of Diocletian.
According to legend, they were employed as carvers at Sirmium (Mitrovica, Yugoslavia) and impressed Diocletian with their art, as did another carver, Simplicius. Diocletian commissioned them to do several carvings, which they did to his satisfaction, but they then refused to carve a statue of Aesculapius, as they were Christians. The emperor accepted their beliefs, but when they refused to sacrifice to the gods, they were imprisoned.
When Diocletian's officer Lampadius, who was trying to convince them to sacrifice to the gods, suddenly died, his relatives accused the five of his death; to placate the relatives, the emperor had them executed. Another story has four unnamed Corniculari beaten to death in Rome with leaden whips when they refused to offer sacrifice to Aesculapius. They were buried on the Via Lavicana and were later given their names by Pope Militiades. Probably they were the four Pannonian martyrs (not counting Simplicius) whose remains were translated to Rome and buried in the Four Crowned Ones basilica there.
A further complication is the confusion of their story with that of the group of martyrs associated with St. Carpophorus in the Roman Martyrology under November 8th.