The Chaos Sea was a very magical place!
This was the space between the Heaven Domain and the Earth Domain; it could be said to be an enormous mystic realm.
Originally, heading to the Heaven Domain from the Earth Domain required ascension; only King-Ranked formidable martial artists could ascend. However, as the Netherworld Realm's assaults on the Heaven Domain grew more severe and the situation grew grim, the powerful men of the Heaven Domain created many formidable Teleportation Formations in the Chaos Sea thousands of years ago. That way, Earth Domain's God Thearch-equivalent formidable martial artists could teleport first to the Chaos Sea and then from there to the Heaven Domain. This way, even if one did not ascend, he could enter the Heaven Domain and join in the battle.
A fog was ever-present in the Chaos Sea. There weren't any huge continents here but islands floating in midair, just like a sea. Hence, this place had been called the Chaos Sea!