A beautiful island kingdom saved by Arthur in Le Chevalier du Papegau.
It’s queen, Flor de Mont, was overthrown and imprisoned by the wicked steward of her late father, King Beauvoisin. The steward imprisoned her in the Fearless Keep and retired himself to the Perilous Castle. Arthur, responding to the queen’s entreaties, slew the steward and saved the kingdom.
Source
Le Chevalier du Papegau | Late 14th century or early 15th century