Leader of the Fianna
Fionn mac Cumhaill was the leader of the Fianna — the roving warrior-band of Ireland — and the man who gained supernatural wisdom by accident as a child and kept it for the rest of his life.
His father was Cumhall, the previous leader of the Fianna, killed by Goll mac Morna in a leadership dispute before Fionn was born. Fionn’s mother Muirne gave the baby to two women to raise in hiding on the slopes of Sliabh Bladma — his aunt Bodhmall the druidess and Liath Luachra the warrior-woman — and he grew up in the hills with his identity concealed until he was old enough to claim what was his.
When he was old enough, he went to study under the poet Finnéces on the bank of the River Boyne. Finnéces had been trying for seven years to catch the Salmon of Knowledge — the fish that had absorbed all the wisdom in the world by eating hazelnuts falling from the nine sacred hazel trees into the Well of Segais. Fionn was set to cook the salmon when it was finally caught, with strict instructions not to eat any. A blister rose on the fish’s skin. He pressed it with his thumb to burst it and put his thumb in his mouth. The wisdom passed through. Finnéces looked at him and knew. The boy’s name — Fionn, the fair one — fulfilled the prophecy Finnéces had been waiting for. He gave the boy the rest of the fish. It was his by destiny.
After that, biting his thumb gave Fionn supernatural insight whenever he needed it. The tradition calls it the fiosaíocht — the thumb-knowledge. It was not a gift from a god or a druidic initiation. It was an accident, permanently fixed in a thumb.
He took his father’s place as leader of the Fianna and set its famously demanding admission standards: memorise twelve books of poetry, defeat nine warriors simultaneously, be able to outrun a deer. The Fianna under Fionn was the tradition’s most complete picture of what a warrior society could look like at its best.
His wife Sadhbh was transformed into a deer by the Dark Druid. She gave him a son — Oisín — before she was taken back. Fionn spent years searching Ireland for her and never found her. His grandson Oscar became the greatest warrior of the later Fianna.
The story that damaged him most was the pursuit of Diarmuid and Gráinne. Gráinne was betrothed to Fionn but put a geis on Diarmuid to take her at the feast. Fionn pursued them across Ireland for years. When Diarmuid finally died of the enchanted boar’s tusk wound at Ben Bulben, Fionn could have healed him — he had only to carry water from the well in his hands. He went to the well. He let the water fall through his fingers. He went again. He let it fall again. The third time, Oscar stood over him with a drawn sword and told him to bring the water or die for withholding it. He came back. Diarmuid was already dead.
He is said to sleep in a cave — sometimes the Cave of Keshcorran, sometimes elsewhere — and will wake to lead Ireland in its hour of greatest need.
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