Like Patrick, Iserninus was born in Roman Britain, but he was apparently a fluent Celtic speaker; perhaps his family stayed with the old language of the Britons instead of fully adopting Latin as their language at home. Tradition says that he was ordained as a deacon at Auxerre in Burgundy along with Patrick and Auxilius. According to the Annals of Ulster, he began his mission to Ireland in 439 AD, and eventually became a bishop.

Histories written in later centuries say that Patrick called on Iserninus and Auxilius to join him in Ireland, to help with the mission there. Patrick assigned him the area just south of what is now Dublin, in Laigin, and current tradition shows his influence in the area. He is said to have founded a church in Aghade, County Carlow, where he was later buried. He also founded a church in Old Kilcullen, where he was appointed a bishop; its location is no doubt related to nearby Dun Ailinne, a ceremonial site of the kings of Leinster. However, his theological training and mastery of the Celtic language no doubt made him a valuable asset when debating the Druids throughout Ireland.

Modern scholarship has unearthed a slightly different story. Historian Charles Thomas says “The weight of current opinion is perhaps in favor of associating Secundinus, Auxilius, and Iserninus with Palladius rather than with Patrick.” This would imply that Iserninus was in Ireland with its first bishop, and may have even started his ministry before Patrick arrived. So why did the story change?

It all comes down to 7^th century politics. During the decades after Ireland converted to Christianity, the different monasteries and churches struggled to assert their claims to be the most important holy site on the island, and to be the seat of the archbishop. The church at Armagh was founded by Patrick at a strategic location, near the ceremonial site of the kings of Ulster. It grew to be a great church, and cherished its connection with Patrick. In order to bolster their prominence, there is evidence that 7^th century monks of Armagh altered the histories, attributing many achievements to Patrick that were really the work of Palladius. So Palladius receded from memory as Patrick was venerated even more, and Armagh grew in prominence. It worked. Today, there is not one, but two cathedrals in Armagh: the seat of the Primate of All Ireland for the Roman Catholic Church and for the Church of Ireland.

Regardless of who he worked most closely with, Iserninus was a key figure in the Christian mission to Ireland. He almost certainly worked with both Palladius and Patrick to bring the new faith to Ireland.

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Historic Characters in Banish the Snakes: Palladius

Historic Characters in Banish the Snakes: Patrick

Historic Characters in Banish the Snakes: Auxilius

Historic Characters in Banish the Snakes: Ciarán