Synadone, Synadoune
The King of Sinadone was one of Arthur’s vassals, and his wife was proven unfaithful by a magic horn in Biket’s Lai du Cor. Biket may have intended Snowdon in Wales.
The Lady of Sinadone is said to have been rescued by Lybius Desconus, who was accompanied by the damsel Ellen. The story appears in the appropriately titled romance Lybius Desconus.
See also
Chastity Test | The Legend of King Arthur
Source
Lai du Cor | Robert Biket, mid to late 12th century