This, meaning the family of Rhys the Deep, is the name given to a tribe of fairy people who inhabited a small land which was invisible because of a certain herb that grew on it.

They were handsome people, rather below the average in height, and it was their custom to attend the market in Cardigan and pay such high prices for the goods there that the ordinary buyer could not compete with them. They were honest and resolute in their dealings, and grateful to people who treated them fairly. One man called Gruffid always treated them so well that they took a great liking to him and invited him to their country, which was enriched with treasures from all over the world. They loaded him with gifts and conducted him back to their boundary. Just before he took leave of them he asked how they guarded all their wealth. Might not even one of their own people betray them into the hands of strangers?

'Oh no', said his guide. 'No snakes can live in Ireland and no treachery can live here. Rhys, the father of our race, bade us, even to the most distant descendant, honour our parents and ancestors; love our own wives without looking at those of our neighbours; and do our best for our children and grandchildren. And he said that if we did so, no one of us would ever prove unfaithful to another, or become what you call a traitor'.

He said that a traitor was an imaginary character with them, shown in a symbolic drawing with the feet of an ass, the head of the devil and a bosom full of snakes, holding a knife in his hand, with which he had killed his family. With that he said goodbye, and Gruffid found himself near his own home, and could no longer see the Country of Plant Rhys.

After this time he prospered in everything and his friendship with the Plant Rhys continued. After his death, however, the farmers became so covetous that the Plant Rhys no longer frequented Cardigan Market, and were said to have gone to Fishguard.

This land of virtuous, honest fairy people is like that visited by Elidor in the story of Elidor and the golden ball in medieval times. John Rhys in Celtic Folk-Lore quotes this account from the Brython (vol.I).