Ecos

Ecos is an aquatic world filled with lush coral reefs and kelp forests bathed by the light of twin suns. Home to an underwater civilization that's divided into 150 city-states. The indigenous species of Ecos are intelligent amphibians called the Ecoi who share the planet with other races who’ve settled on the planet. The surface consists of 97% water, and those without aquatic respiratory systems live in eco dome homes.

Religion
Mystic teaching of the people of Ecos: Mystic waters hold memory

Heavily isolated from the surface is the Citadel. The Ecoi are very spiritual. They're the two most sacred places being the Citadel and the Garden, both off-limits to outsiders. To violate this decree is to go against the people of Ecos, punishable by death.

The Library of The Scrolls
Ecos is also home to the Library of The Scrolls, once known as the Sacred College, currently, one of the biggest and oldest reliquaries in space holding the most dangerous and forbidden knowledge.