Tarcisius was a young acolyte of the Roman Church during the persecution of Valerian. Pope Damasus I, writing in the 4th century, recorded the story on an inscription in the Catacombs of San Callisto: the boy was carrying the Blessed Sacrament to imprisoned Christians awaiting martyrdom when he was set upon by a band of pagans on the Appian Way.
When they tried to seize the Eucharist from him, he fought them off, refusing to surrender it; they beat and stoned him to death. The Eucharist was found untouched on his body — by Damasus's account, 'not even a fragment of the sacred form was found on him: the pious boy preferred to give his life rather than expose to the rage of dogs the Body of Christ.'
He is among the patron saints of altar servers and First Communicants. His example formed countless Catholic boys in devotion to the Eucharist; the novel Fabiola by Cardinal Wiseman (1854) and the lives by Daniel Considine SJ made his story one of the best-known of the early Roman martyrs in the 19th and 20th centuries.