The Duarl Sea (analogue to the real-world Iroise Sea) is a part of the Atlas Ocean located off the coast of the Promalock area, on the Gllia Region of the continent of Eresia. The island of Esteria and its surrounding Stormwall lie amidst this sea.
The Duarl Sea is explored by adventurer Adol Christin during the backstory of Ys I: Ancient Ys Vanished and Ys IV: Mask of the Sun.