But the Shadow turned and fled before him, and Finn chased it northward to the Fairy Mound of Slieve Fuad, and there he drove the spear through its back.

And what it was that fell there in the night, and what it was that passed like the shadow of a shadow into the Fairy Mound, none can tell, but Finn bore back with him next day a pale, sorrowful head on the point of Fiacha's spear, and the goblin troubled the folk of royal Tara no more.
But Conn of the Hundred Battles called the Fianna together, and he set Finn at his right hand and said, "Here is your Captain by birth-right and by sword-right.

Let who will now obey him hence-forward, and who will not, let him go in peace and serve Arthur of Britain or Arist of Alba, or whatsoever King he will." And Goll, son of Morna, said, "For my part I will be Finn's man under thee, O King," and he swore obedience and loyalty to Finn before them all.

Nor was it hard for any man to step where Goll had gone before, so they all took their oaths of Fian service to Finn mac Cumhal.

And thus it was that Finn came to the captaincy of the Fianna of Erinn, and he ruled the Fianna many a year till he died in battle with the Clan Urgrenn at Brea upon the Boyne..