A stronger tradition, however, celebrates Iarlaithe son of Lug as teacher of a subsequent generation of church founders, and associates him with a school at Cluain Fois (near Tuam, Co. Galway). His students included Brendan (qv) of Clonfert, according to the Latin Life of the latter. It is related that the elderly bishop was helped to find the ‘place of his resurrection’ (the foundation at which he would be buried) by the young Brendan. When a wheel gave way beneath his chariot, Iarlaithe interpreted this as a divine message and so established the church of Tuaim dá Gualann (Tuam) at the location concerned.
Although John Colgan (qv) placed his floruit around the middle of the sixth century, the year of Iarlaithe's death is not recorded; he probably died on 26 December, under which date he is commemorated in the martyrologies. His relics were long preserved at the chapel of Scrín in Tuam. His church assumed a primacy amongst the bishoprics of Connacht; it was formally designated as a metropolitan see at the synod of Kells–Mellifont (1152).