[3] Their legend states that they were martyred at Rome under the Emperor Diocletian towards the end of the third century, most likely in the year 286.

Sebastian converted Tranquillinus and Martia, as well as Tiburtius, the son of Agrestius Chromatius, allegedly prefect of Rome.

Mark and Marcellian were concealed by Castulus, a Christian officer, but they were betrayed by an apostate, Torquatus.

Chromatius's alleged successor Fabianus[5] condemned them to be bound head downwards to two pillars with their feet nailed to them.

Meanwhile, Zoe was hung to the branch of a tree and a fire was kindled underneath her feet, and she was killed.

[6] The bodies of Marcus and Marcellianus were moved, probably during the ninth century, to the Church of Santi Cosma e Damiano.

[4] The bodies remain there in a tomb, near an ancient painting of the two martyrs with a third person, who appears to be the Virgin Mary.