Long, long ago, the Emperor of Non-Beginning went to the Realm Sea of a certain domain for training.
Suddenly, an immense beast appeared, emerging from the rift of time and space, swallowing the entire Realm Sea in one gulp. Fortunately, he noticed something was amiss and desperately fled the Realm Sea, or else he might have been swallowed by the giant beast.
Throughout the process, he never saw the true form of this opponent because its body was too enormous, so vast that the entire Realm Sea could not accommodate even a part of it. Thus... from the perspective of the Emperor of Non-Beginning, it seemed like the sky turned into an abyssal maw, devouring the entire Realm Sea!
Having escaped the Realm Sea, the Emperor of Non-Beginning was left with lingering fears.
This Realm Sea, within the Ten Thousand Realms, was considered exceptionally immense, belonging to the medium-lower tier of Realm Seas, containing tens of thousands of Great Worlds and many small worlds.
