Culhwch and Olwen, a tale from

The Mabinogion

…..."It will be best," said they, "to seek Mabon the son of Modron; and he will not be found unless we first find Eidoel, the son of Aer, his kinsman." Then Arthur rose up, and the warriors of the Islands of Britain with him, to seek for Eidoel; and they proceeded until they came before the Castle of Glivi, where Eidoel was imprisoned. Glivi stood on the summit of his castle, and he said, "Arthur, what requirest thou of me, since nothing remains to me in this fortress, and I have neither joy nor pleasure in it; neither wheat nor oats? Seek not therefore to do me harm." 
Said Arthur, "Not to injure thee came I hither, but to seek for the prisoner that is with thee." 

"I will give thee my prisoner, though I had not thought to give him up to any one; and therewith shalt thou have my support and my aid."

His followers said unto Arthur, "Lord, go thou home, thou canst not proceed with thy host in quest of such small adventures as these." 

Then said Arthur, "It were well for thee, Gwrhyr Gwalstawd Ieithoedd, to go upon this quest, for thou knowest all languages, and art familiar with those of the birds and the beasts. Thou, Eidoel, oughtest likewise to go with my men in search of thy cousin. And as for you, Kai and Bedwyr, I have hope of whatever adventure ye are in quest of, that ye will achieve it. Achieve ye this adventure for me."

They went forward until they came to the Ousel of Cilgwri. And Gwrhyr adjured her for the sake of Heaven, saying, "Tell me if thou knowest aught of Mabon the son of Modron, who was taken when three nights old from between his mother and the wall." 

And the Ousel answered, "When I first came here, there was a smith's anvil in this place, and I was then a young bird; and from that time no work has been done upon it, save the pecking of my beak every evening, and now there is not so much as the size of a nut remaining thereof; yet the vengeance of Heaven be upon me, if during all that time I have ever heard of the man for whom you inquire. Nevertheless I will do that which is right, and that which it is fitting that I should do for an embassy from Arthur. There is a race of animals who were formed before me, and I will be your guide to them."

So they proceeded to the place where was the Stag of Redynvre. "Stag of Redynvre, behold we are come to thee, an embassy from Arthur, for we have not heard of any animal older than thou. Say, knowest thou aught of Mabon the son of Modron, who was taken from his mother when three nights old?......

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