As depicted in Rankin-Bass's adaptation of The Life and Adventures of Santa Claus
The King of the Ryls is an immortal, and the ruler of the Ryls. He lives among the gay flowers and luscious fruits of Valencia. A Prince rules his people in the Forest of Burzee.
The King was part of the Council of Immortals that bestowed upon Santa Claus the Mantle of Immortality. (The Life and Adventures of Santa Claus)
The King of the Ryls is a personal friend of Prince Marvel — or rather, of the fairy who became Prince Marvel for a year. (The Enchanted Island of Yew)