Fionn had many wives and sweethearts, one of them, Saar, being mother of Oisin. Saar was turned into a fawn by a Druid, and fled from Fionn's house. Long after he found a beast-child in the forest and recognised him as his son. He nourished him until his beast nature disappeared, and called him Oisin, "little fawn." Round this birth legend many stories sprang up—a sure sign of its popularity.511 Oisin's fame as a poet far excelled that of Fionn, and he became the ideal bard of the Gaels.
By far the most passionate and tragic story of the saga is that of Diarmaid and Grainne, to whom Fionn was betrothed. Grainne put geasa upon Diarmaid to elope with her, and these he could not break. They fled, and for many days were pursued by Fionn, who at last overtook them, but was forced by the Fians to pardon the beloved hero. Meanwhile Fionn waited for his revenge. Knowing that it was one of Diarmaid's geasa never to hunt a wild boar, he invited him to the chase of the boar of Gulban. Diarmaid slew it, and Fionn then bade him measure its length with his foot. A bristle pierced his heel, and he fell down in agony, beseeching Fionn to bring him water in his hand, for if he did this he would heal him. In spite of repeated appeals, Fionn, after bringing the water, let it drip from his hands. Diarmaid's brave soul passed away, and on Fionn's character this dire blot was fixed for ever.512
Other tales relate how several of the Fians were spirited away to the Land beyond the Seas, how they were rescued, how Diarmaid went to Land under Waves, and how Fionn and his men were entrapped in a Fairy Palace. Of greater importance are those which tell the end of the Fian band. This, according to the annalists, was the result of their exactions and demands. Fionn was told by his wife, a wise woman, never to drink out of a horn, but coming one day thirsty to a well, he forgot this tabu, and so brought the end near. He encountered the sons of Uirgrenn, whom he had slain, and in the fight with them he fell.513 Soon after were fought several battles, culminating in that of Gabhra in which all but a few Fians perished. Among the survivors were Oisin and Caoilte, who lingered on until the coming of S. Patrick. Caoilte remained on earth, but Oisin, whose mother was of the síd folk, went to fairyland for a time, ultimately returning and joining S. Patrick's company.514 But a different version is given in the eighteenth century poem of Michael Comyn, undoubtedly based on popular tales. Oisin met the Queen of Tir na n-Og and went with her to fairyland, where time passed as a dream until one day he stood on a stone against which she had warned him. He saw his native land and was filled with home-sickness. The queen tried to dissuade him, but in vain. Then she gave him a horse, warning him not to set foot on Irish soil. He came to Ireland; and found it all changed. Some puny people were trying in vain to raise a great stone, and begged the huge stranger to help them. He sprang from his horse and flung the stone from its resting-place. But when he turned, his horse was gone, and he had become a decrepit old man. Soon after he met S. Patrick and related the tale to him.
Of most of the tales preserved in twelfth to fifteenth century MSS. it may be said that in essence they come down to us from a remote antiquity, like stars pulsing their clear light out of the hidden depths of space. Many of them exist as folk-tales, often wild and weird in form, while some folk-tales have no literary parallels. Some are Märchen with members of the Fian band as heroes, and of these there are many European parallels. But it is not unlikely that, as in the case of the Cúchulainn cycle, the folk versions may be truer to the original forms of the saga than the rounded and polished literary versions. Whatever the Fians were in origin—gods, mythic heroes, or actual personages—it is probable that a short Heldensage was formed in early times. This slowly expanded, new tales were added, and existing Märchen formulæ were freely made use of by making their heroes the heroes of the saga. Then came the time when many of the tales were written down, while later they were adapted to a scheme of Irish history, the heroes becoming warriors of a definite historic period, or perhaps connected with such warriors. But these heroes belonged to a timeless world, whose margins are "the shore of old romance," and it was as if they, who were not for an age but for all time, scorned to become the puppets of the page of history.
The earliest evidence of the attitude of the ecclesiastical world to these heroes is found in the Agallamh na Senorach, or "Colloquy of the Ancients."515 This may have been composed in the thirteenth century, and its author knew scores of Fionn legends. Making use of the tradition that Caoilte and Oisin had met S. Patrick, he makes Caoilte relate many of the tales, usually in connection with some place-name of Fian origin. The saint and his followers are amazed at the huge stature of the Fians, but Patrick asperges them with holy water, and hosts of demons flee from them. At each tale which Caoilte tells, the saint says, "Success and benediction, Caoilte. All this is to us a recreation of spirit and of mind, were it only not a destruction of devotion and a dereliction of prayer." But presently his guardian angel appears, and bids him not only listen to the tales but cause them to be written down. He and his attendant clerics now lend a willing ear to the recital and encourage the narrator with their applause. Finally, baptism is administered to Caoilte and his men, and by Patrick's intercessions Caoilte's relations and Fionn himself are brought out of hell. In this work the representatives of paganism are shown to be on terms of friendliness with the representatives of Christianity.
But in Highland ballads collected in the sixteenth century by the Dean of Lismore, as well as in Irish ballads found in MSS. dating from the seventeenth century onwards, the saint is a sour and intolerant cleric, and the Fians are equally intolerant and blasphemous pagans. There is no attempt at compromise; the saint rejoices that the Fian band are in hell, and Oisin throws contempt on the God of the shaven priests. But sometimes this contempt is mingled with humour and pathos. Were the heroes of Oisin's band now alive, scant work would be made of the monks' bells, books, and psalm-singing. It is true that the saint gives the weary old man hospitality, but Oisin's eyes are blinded with tears as he thinks of the departed glories of the Fians, and his ears are tormented "by jangling bells, droning psalms, and howling clerics." These ballads probably represent one main aspect of the attitude of the Church to Celtic paganism. How, then, did the more generous Colloquy come into being? We must note first that some of the ballads have a milder tone. Oisin is urged to accept the faith, and he prays for salvation. Probably these represent the beginning of a reaction in favour of the old heroes, dating from a time when the faith was well established. There was no danger of a pagan revival, and, provided the Fians were Christianised, it might be legitimate to represent them as heroic and noble. The Colloquy would represent the high-water mark of this reaction among the lettered classes, for among the folk, to judge by popular tales, the Fians had never been regarded in other than a favourable light. The Colloquy re-established the dignity of the Fian band in the eyes of official Christianity. They are baptized or released from hell, and in their own nature they are virtuous and follow lofty ideals. "Who or what was it that maintained you in life?" asks Patrick. And Caoilte gives the noble reply, "Truth that was in our hearts, and strength in our arms, and fulfilment in our tongues."