When Saint Finnian was in extremis, suffering from the plague, Columba administered Holy Viaticum. Having completed his studies, he took charge of Saints Caemban, Fintan, and Mocumin. He founded the celebrated monastery of Tirdaglas (Tir-da-glasí), or Terryglass in 548. It is said that he visited Tours and brought from there the relics of St. Martin of Tours.
He died of the plague on 13 December 552, and was buried within the precincts of his own monastery at Terryglass. Some fifteen other saints of Ireland, bearing the name Columba, are mentioned in the Martyrology of Gorman.