|Citadel of the Sea
Isles of the Blessed
Thalasia is the origin layer of the River Oceanus that flows though the other layers. The layer is dotted with islands, known collectively as the Isles of the Holy Dead, the Isles of the Blessed, the Hills of Avalon, the Islands beyond the World, and the Heroic Isles.
Godly realms on this layer include, O-Wata-Tsu-Mi's realm of Citadel of the Sea, Belenus and Brigantia's shared realm of Isles of the Blessed, selkie deity Surminare's realm of Selkies' Grotto. Trishina can be found wandering on Thalasia when not with her consort, Deep Sashelas.