The island where Balin and Balan killed each other. Merlin created many marvels on the island, including the second Sword in the Stone, which floated up to Camelot before the Grail Quest.
The island was also known as the Island of Marvels.
See also
Balin’s Sword | The Legend of King Arthur
Source
Post-Vulgate Suite du Merlin | 1230-1240
