Kilhwch, the son of Kilydd, prince of Kelyddon, having heard some one mention the name of Olwen, daughter of Yspaddaden Penkawr, falls violently in love, without having ever seen her.  He goes to find Arthur, that he may ask for his aid in the difficult undertaking which he meditates; in point of fact, he does not know in what country the fair one of his affection dwells.  Yspaddaden is besides a frightful tyrant who suffers no man to go from his castle alive, and whose death is linked by destiny to the marriage of his daughter. [Footnote:  The idea of making the death of the father the condition of possession of the daughter is to be found in several romances of the Breton cycle, in Lancelot for example.] Arthur grants Kilhwch some of his most valiant comrades in arms to assist him in this enterprise.  After wonderful adventures the knights arrive at the castle of Yspaddaden, and succeed in seeing the young maiden of Kilhwch’s dream.  Only after three days of persistent struggle do they manage to obtain a response from Olwen’s father, who attaches his daughter’s hand to conditions apparently impossible of realisation.  The performance of these trials makes a long chain of adventures, the framework of a veritable romantic epic which has come to us in a very fragmentary form.  Of the thirty-eight adventures imposed on Kilhwch the manuscript used by Lady Guest only relates seven or eight.  I choose at random one of these narratives, which appears to me fitted to give an idea of the whole composition.  It deals with the finding of Mabon the son of Modron, who was carried away from his mother three days after his birth, and whose deliverance is one of the labours exacted of Kilhwch.

“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 all the vengeance of Heaven be upon me, if during all that time I have ever heard of the man for whom you enquire.  Nevertheless I will do that which is right, and that which it is fitting 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.”