Out of the 12 Apostles, St. John stands alone as the only one who did not die a martyr's death. He lived to a ripe old age and reportedly died of natural causes.
According to tradition, he died around 100 AD and is buried near Ephesus. It is believed that after Jesus entrusted his mother Mary to John, they moved to Ephesus after Jesus' resurrection. There they lived until Mary was assumed into Heaven.
But without danger?
A legend celebrated in art tells of John being offered a poisoned chalice by enemies of the new faith, but drinking safely from it. In art, he is often depicted holding a cup from which a serpent escapes.
There is also another tradition that claims St. John was exiled on the island of Patmos, Greece. The author of the book of Revelation, who is often connected to St. John the Apostle, writes, “I John, your brother, who share with you in Jesus the tribulation and the kingdom and the patient endurance, was on the island called Patmos on account of the word of God and the testimony of Jesus” (Revelation 1:9).
This would mean that St. John did experience persecution, but was exiled, instead of killed.
St. John before the Latin Gate
The reason for his exile is linked to another legendary story that connects St. John the Apostle to an event that would have normally made him a martyr.
Dom Prosper Gueranger sets-up the story in his Liturgical Year:
John, the august founder of the Seven Churches of Asia Minor, appeared before the Tribunal of pagan Rome. He was convicted of having propagated in a vast province of the Empire the worship of a Jew that had been crucified under Pontius Pilate. He was a superstitious and rebellious old man and it was time to rid Asia of his presence. He was therefore sentenced to an ignominious and cruel death. He had somehow escaped Nero's power but he should not elude the vengeance of Cæsar Domitian.
Gueranger continues with what surely would have been the end of St. John:
A huge cauldron of boiling oil is prepared in front of the Latin Gate. The sentence orders that the preacher of Christ be plunged into this bath. The hour is come for the second son of Salome to partake of his Master's Chalice.
St. John is thrown into the cauldron but, "lo, the boiling liquid has lost all its heat. The Apostle feels no scalding -- on the contrary -- when they take him out again, he feels all the vigor of his youthful years restored to him."
An imperial decree then exiles him to the island of Patmos due to his supernatural survival.
A Church was reportedly built on the site of this event and the Church formerly celebrated a universal feast of St. John before the Latin Gate on May 6 every year.