Titans, the alien beings that created the Cosmos. The Greeks view him as the embodiment of the waters that surround the known world. In actuality, his vast, inhuman intellect is encoded in the quantum fabric of spacetime--the "ocean" outside the Earth. The Olympians believe that Okeanos was not a collaborator with Kronos's experiment, but was trapped in the nascent cosmos structure and compressed into his current role.
His "wife" (if such a term is really applicable to such beings) Tethys, also resides primarily in spacetime but is considered a separate being--or at least exists at separate energy state.
Their creations/partial avatars/children (again, the exact relationship is difficult to describe in human terms) are known as Oceanids. Most are equally at home in the icy Oort Cloud as the depths of Earth's oceans. Whatever their appearance, they approach the Olympians in terms of power and exceed them in some capabilities.
Since he was integral to the Cosmos (and apparently no partisan of Kronos), the Olympians didn't imprison Okeanos--though it 's unlikely they could have in any case. His manifestation appears as a giant humanoid male made from the very night sky he stepped out of. He seldom appears on Earth, though, and what little communication he has with humans is in dreams.
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