But Finn never really forgave, and, soon after, he urged Diarmait to go out to the chase of the wild boar of Benn Gulban[[254]]. Diarmait killed the boar without getting any hurt; for, like the Greek Achilles, he was invulnerable, save in his heel alone. Finn, who knew this, told him to measure out the length of the skin with his bare feet. Diarmait did so. Then Finn, declaring that he had measured it wrongly, ordered him to tread it again in the opposite direction. This was against the lie of the bristles; and one of them pierced Diarmait’s heel, and inflicted a poisoned and mortal wound.
This “Pursuit of Diarmait and Grainne”, which has been told at such length, marks in some degree the climax of the Fenian power, after which it began to decline towards its end. The friends of Diarmait never forgave the treachery with which Finn had compassed his death. The ever-slumbering rivalry between Goll and his Clann Morna and Finn and his Clann Baoisgne began to show itself as open enmity. Quarrels arose, too, between the Fenians and the High-Kings of Ireland, which culminated at last in the annihilation of the Fianna at the battle of Gabhra[[255]].
This is said to have been fought in A.D. 284. Finn himself had perished a year before it, in a skirmish with rebellious Fenians at the Ford of Brea on the Boyne. King Cormac the Magnificent, Grainne’s father, was also dead. It was between Finn’s grandson Oscar and Cormac’s son Cairbré that war broke out. This mythical battle was as fiercely waged as that of Arthur’s last fight at Camlan. Oscar slew Cairbré, and was slain by him. Almost all the Fenians fell, as well as all Cairbré’s forces.
Only two of the greater Fenian figures survived. One was Caoilte, whose swiftness of foot saved him at the end when all was lost. The famous story, called the “Dialogue of the Elders”, represents him discoursing to St. Patrick, centuries after, of the Fenians’ wonderful deeds. Having lost his friends of the heroic age, he is said to have cast in his lot with the Tuatha Dé Danann. He fought in a battle, with Ilbhreach son of Manannán, against Lêr himself, and killed the ancient sea-god with his own hand.[[256]] The tale represents him taking possession of Lêr’s fairy palace of Sídh Fionnechaidh, after which we know no more of him, except that he has taken rank in the minds of the Irish peasantry as one of, and a ruler among, the Sídhe.
The other was Ossian, who did not fight at Gabhra, for, long before, he had taken the great journey which most heroes of mythology take, to that bourne from which no ordinary mortal ever returns. Like Cuchulainn, it was upon the invitation of a goddess that he went. The Fenians were hunting near Lake Killarney when a lady of more than human beauty came to them, and told them that her name was Niamh[[257]], daughter of the Son of the Sea. The Gaelic poet, Michael Comyn, who, in the eighteenth century, rewove the ancient story into his own words,[[258]] describes her in just the same way as one of the old bards would have done:
“A royal crown was on her head;
And a brown mantle of precious silk,
Spangled with stars of red gold,
Covering her shoes down to the grass.
“A gold ring was hanging down