Nath Í mac Fiachrach

Most early Irish sources, including the Lebor Gabála Érenn,[3] the Annals of the Four Masters[4] and Geoffrey Keating's Foras Feasa ar Éirinn,[5] place him in the traditional list of High Kings of Ireland, after Niall of the Nine Hostages and before Niall's son Lóegaire, with Nath Í's son, Ailill Molt, succeeding Lóegaire.

Later writers, presuming this to be his death notice, added the detail that he was struck by lightning in the Alps,[1] circumstances also recounted in the Lebor Gabála,[3] Keating[5] and the Annals of the Four Masters, the latter of which dates it to 428.

[4] According to legend, his followers carried his body back to Ireland, winning ten battles on the way, and buried him at Cruachan, capital of Connacht.

77–78  [3][5] A standing stone said to mark his grave is part of the Rathcroghan complex of archeological sites near Tulsk in County Roscommon.

[1] O'Rahilly therefore concludes that "he was a king of Connacht in the first half of the fifth century, that he appears to have acquired fame in his day as a leader of predatory expeditions to Britain, and that he died in or about the year 445, and was probably buried at Cruachain.

[10] A fuller version of his death-tale, as mentioned to in the annals, is found in the saga Aided Nath Í ("the death of Nath Í"), a later version of the Lebor Gabála, and Keating, in which he besieges a tower in which Forménus, king of Thrace, lives as a hermit, having forsaken his kingdom for a religious life.