Saint Marcellus was a centurion stationed at Tingis (also known now as Tangiers). In the year 298, the birthday of Emperor Maximin Hercules was celebrated with extraordinary feasting and grandiose sacrifices to the Roman Gods in the Emperor's name. Saint Marcellus refused to participate in these sacrifices and threw down his military belt, arms and vine-branch (the mark of his post of Centurion, an insignia of his rank - Roman soldiers were forbid to strike soldiers with anything except a vine-branch) down onto the ground.
The non-Christian soldiers of his regiment called forth the prefect of the legion Anastasius Forunatus. It is recorded that Saint Marcellus said to him:
"When you celebrated the emperor's festival on the 12th before the calends of August, I said aloud that I was a Christian, and could serve no other than Jesus Christ, the Son of God."
Fortunatus ordered him to be taken before the Emporer Maximian and Constantius, but was brought first to the deputy Praetorian prefect Aurelius Agricolanus. When asked if he had committed the crime in the letter, Saint Marcellus said yes and was immediately sentenced to death. He was martyred with a sword. Tradition holds that the official secretary of the court, Saint Cassian was so angry about the incident that he refused to write down the events. Saint Cassian too was martyred by the prefect.
Saint Marcellus's relics were brought to and enshrined at Leon. The Plaza de San Marcelo in the city was named after him him. Saint Marcellus's feast day in the Roman Calendar is October 30th.