The Plane of Existence is a flat plane of indestructible glass reaching out to infinity in all directions and is approximately a foot thick. The only exception is the hole in its center, which the Sands of Time flow through. This confluence is known as Limbo. The Plane of Existence is what separates the dead from the living, as the Spirit Realm, The Labyrinth, and Olympus are built above it, while The Duat, Heaven, and Hell are built below it. Limbo and the Sands of Time are the only known entities to exist on BOTH sides of the Plane of Existence. If a living person's full body were to fall below the Plane of Existence, their entire body would go numb and they would die. The only way to move above or below the Plane of Existence is to go through the hole that the Sands of Time fall through. However, this is a one-way valve, as those who have already fallen through it and died cannot go back up. The only way to do that would be to somehow restore life to that person's physical body. When the Man of Light and Shadow enters Shadow Mode, it is said that the location they envision in their head is the Plane of Existence. The only location with a direct connection to the Plane of Existence is Limbo.