Synopsis: A parody of "The Mabinogian". This might be referencing the Evangeline Walton version, which came out only a few years earlier. However, the author was a Tolkien scholar, and would have been familiar with older versions of this story. The references to the "Purple Book" in the story are references to the "White Book", and possibly the "Red Book", which are the two oldest known versions of the legend. So far as I remember, those sources are not mentioned in Walton's books, which would imply that this is a parody of older versions.