The second layer of Arborea is Ossa to the Olympians, but it has as many names as the ocean. It's called Aquallor byt the elves, the Endless River by the selkies, and the Green Sea or the Abiding Sea by the creatures of Amun-thys. Its gates are usually found in the watery domains of Deep Sashelas of the elves and Poseidon of the Greeks. Ossa is the outflow of the river Oceanus which flows from the farthest layer of Elysium, Thalasia.
Some cutters spin tales about huge, funnellike maelstroms that lead directly back to Thalasia in an unending circle. Unlike Thalasia, and the waters of Lunia on the first layer of Mount Celestia, the seas of Ossa are shallow for the most part, no more than three feet deep over most of the realm. Great chasms open up in random places here, and the chaotic good sea powers make their domains in these.