Tuan mac Cairill

In Irish mythology Tuan mac Cairill was a recluse who retains his memories from his previous incarnations, going back to Antediluvian age.

Through a series of animal transformations he survived into Christian times, and, in conversation with St. Finnian of Moville told a brief history of himself and of Ireland from his people onward to the coming of St. Patrick.

[2] Tuan who was a hermit or recluse, told St. Finnan that he was born 2000 years earlier and witnessed many of the waves of invaders who came to ancient Ireland - the Nemedians, Fir Bolg and the Tuatha De Dannan.

And he witnessed the invasion of Nemed (who he says was his father's brother), and woke up one day to find himself reborn as a vigorous young stag.

[5] The ancient stag watched the Nemedians perish, and was again reborn into a young wild boar, and became the king of the boar-herds, witnessing the taking of Ireland by Semion, leader of the Fir Bolg.