According to tradition, prior to his conversion to Christianity Eustace was a Roman general named Placidus, who served the emperor Trajan.
One day, while he was pursuing a large deer, it suddenly turned and stood still. Placidus was astonished to see between its antlers a Crucifix, surrounded by a bright light, and to hear from its mouth the same words which our Lord had spoken to Saul, the persecutor of the first Christians: “Placidus, why dost thou persecute me? I am Jesus, who died for love of thee, and who will save thee.” Placidus, greatly surprised, fell upon his knees and said: “What dost thou wish me to do?” “Go into the city,” was the answer; seek a priest, and be baptized, with thy wife and children; and then return hither.”
Placidus obeyed the heavenly voice, went into the city, sought and found a priest, who instructed and baptized him, his wife, and his two sons. Placidus received in baptism the name of Eustace (Greek: Ευστάθιος (Eustáthios), “well stable”, or Ευστάχιος (Eustáchios), “fruitful/rich grain”). His wife, who had been called Tatiana, was named Theopista; the elder son, Agapius, and the younger, Theopistus. After this had taken place, Eustace returned into the forest, humbly praying that God would further make His holy will known to him. The Saviour appeared to him as before, saying: “Thou hast done well; thou hast been obedient. Now, being a Christian, prepare thyself to suffer. A great struggle is approaching; but fear not; be constant. I give thee the assurance of my assistance, and promise thee the crown of eternal glory.”
After their conversion, disasters befell the family: Eustace lost his property and saw his wife and children carried off by Imperial Romans. Not long after, finally restored to his former position, he was also reunited with his family.
One day, Adrian, The Emperor, who ascribed to the gods the victory his army had won over the enemy, appointed a day of thanksgiving, when great sacrifices should be offered to them. All the officials of the state and army were commanded to take part in the solemn rite. The day came, and of all those who had been ordered to be present, Eustace alone was absent. The Emperor desired to know the reason, and dispatched a messenger to Eustace, who returned the answer that, being a Christian, he could not participate in a pagan sacrifice. Enraged at this, the Emperor immediately ordered Eustace, his wife and sons, to be imprisoned.
Afterwards, The Emperor tried with kindness and promises, to win Eustace to worship the gods, but when he found that all was in vain, he had him, with his wife and sons, cast before lions. The beasts, however, forgot their cruelty, and lying down at the feet of the holy confessors, would not harm them.
Adrian, more cruel than the wild beasts of the forest, ordered the Saint, his holy wife and faithful sons, to be thrown into an immense brazen bull, made red-hot. The inhuman sentence was executed. The holy martyrs, by Divine power, remained alive for three days, praising and blessing the great Giver of life and death. At last, when their voices ceased, the bull was opened, and all four were found without life, but also without any injury to their bodies or garments. This glorious martyrdom took place in the year 120.