Owain was the son of Urien and a warrior of King Arthur. He once set out to find the mysterious Black Knight who defeated Cynon, a fellow warrior. He was able to find the knight, but nearly became a prisoner within a castle that the knight fled to. A woman named Luned saved Owain, giving him a ring of invisibility. The Black Knight died of his wounds and Owain married his widow, becoming master of the Castle of the Fountain, where the Black Knight lived. King Arthur sent his knights to find the long parted Owain, and Owain returned with them, eventually forgetting about his wife and the castle.
The very angry woman came to court and accused Owain of treachery and unfaithfulness and Owain became ashamed. He fled to the woods where he lived as a hermit until a well-born lady restored his health. Owain then slew a dragon and befriended a lion, with whom he had numerous adventures. They saved Luned from a fiery death. Eventually Owain returned to the Castle of the Fountain and made up with his wife, where they lived “happily ever after.”