Oceanic Abyss
Sometimes just called the Abyss, for short, the deepest trenches of the ocean stretch all the way out from beneath Atlantis to the edges of the world. These darkened places to which no sunlight ever goes are mostly unexplored due to the crushing depths. Oceanic scholars surmise that there are creatures down in the oceanic abyss and postulate it may be where krakens and sea serpents originate. Scholars of magic also surmise that there may be literal portals to the actual demonic Abyss and similar planes down in that darkness.