To travel from the Border Ethereal to the Deep Ethereal, a creature must will themselves to the Deep Ethereal and find the color curtain that will transport them into the Deep. For travelers going through the Deep Ethereal, not only must they physically move through the mists, but they must also will themselves to their destination, picturing it in their mind. This is a long process that might require several days or hundreds of hours of walking to journey from a Border Ethereal bordering the Material World to a Border bordering the Plane of Fire. If a creature decides to walk through the Deep Ethereal without a clear picture in their head of the destination, they will never find a way out of the Deep Ethereal and live out the rest of their days in its roiling mists.

Protomatter

The mists of the Ethereal are made up of existence itself, though it doesn’t take on a specific appearance but rather appears as a dense fog that is white and blue-tinged. This material is thought to be reality, the material that creates the planes and makes ideas and laws of the universe real. This material is more than just an abstraction, but reality as those with the mind to do so can shape and collect this matter in the Ethereal Plane. This material comes in three different forms: Ephemeral, Quintessential, and Stable.

While the material is Ephemeral, it is light and fluffy like a snowflake and is easy to walk through and not even notice on your journeys. This material flows through the Ethereal Plane as if stirred up by a wind and can be compacted into the next form. Quintessential feels like heavy, dense cork and is protomatter in a temporary state of physicalness. Quintessential can form quickly when too much Ephemeral matter sticks together or by a willful creature trying to produce a solid object out of matter, though this form is always temporary. Stable matter feels like metal sheathed in thin layers of leather and is stable for eons unless forced back into its previous states. While this Stable matter floats through the Ethereal Plane, it slowly gathers more and more matter, building larger and larger bergs of Stable matter.

Locations

The Ethereal Plane is often compared to an ocean, its strange mists and fogs making it a strange and alien location. The Border, in this analogy, is the shallow waves on the beach while the Deep Ethereal is the deep ocean filled with strange and unique creatures. Occasionally the ocean is broken up by islands, the demiplanes, that are created out of protomatter by an unknown force strong enough to create worlds in reality. To travel from one sandy shore to another always requires you to swim through the deep ocean, braving hidden dangers that lurk in the mists.

Border

There is no single Border Ethereal, but rather almost every plane and demiplane that the Ethereal Plane touches, has its own Border. While on the Border Ethereal of a plane, you can see the adjacent world as if looking through a glazed and cloudy window, tiny details are largely obscured and your vision doesn’t go much further than 60 feet while here. You can see the adjacent world while you reside on the Border, though objects and people are made up of multi-colored fogs and almost no sound can ever escape from the plane to the Border.

While you are on the Border Ethereal, you are completely invisible to those on the adjacent plane unless they have some magical means of seeing you. Spies and assassins use this ability to glean information, to bypass walls and guards, and to ambush their prey. Depending on the plane you are bordering, the Border may see a lot of traffic, the Inner Planes see many genies moving through the Border and Deep Ethereal.

Every Border can behave differently based on what plane you are bordering on, with every Border taking on traits that bleed over from the adjacent worlds. The Material Worlds are largely safe to visit, though visiting the Border of the Plane of Lightning might give you horrible shocks the longer you stay in it, whereas the Border of the Positive Energy Plane may fill you with so much life that you explode in radiant energy.

Deep

While there are multiple Borders, there is only one Deep Ethereal where all travelers must journey through if they hope to reach another world. To arrive in the Deep Ethereal, you must leave the Border through a color curtain, similar to the color pools of the Astral Plane or cast a spell to immediately transport you here. These curtains appear to be glittering lights in different colors depending on where you are going to, and hover in the air, slowly moving as if by an unfelt wind.

While in the Deep Ethereal, visibility is severely limited and dangers unknown lurk in its mist-filled depths. There is no ground, though luckily a sort of gravity can be felt, allowing for groups to quickly orientate themselves with it. Traveling from one Border to another Border is a dangerous proposition and could take several hundred hours of moving towards your goal. Due to how long this takes, and that there is no natural sustenance to be found in the Deep, travelers must come prepared for travel that might take them over a month to finish.

Many claim that the Ethereal Plane is far more populated than the Astral Plane, though it can be difficult to tell due to the severely limited vision provided on the plane. For this reason, travelers are recommended to stick together in groups, no one should wander off on their own, and you should be on guard at all times. Strange creatures, with many of them never having been seen before, lurk in the thick mists.

Demiplanes

While the Ethereal Plane is separated into two distinct locations, the Border Ethereal and the Deep Ethereal, there are also smaller locations known as Demiplanes that seem to have been created out of nowhere in the Ethereal Plane. Many believe that these demiplanes were created by massive clusters of Stable protomatter that grew so large that it created a demiplane in the Deep Ethereal, though others dispute such claims.

Regardless of how they form, they are all different with their own realities. Some demiplanes may be a massive writhing mass of worms, another may have severely powerful gravity, and another may even have two Border Ethereals. Every Demiplane twists and distorts reality, and many of them feature hidden dangers that swallow up travelers.

The Black Abyss

This demiplane is in a permanent state of decay and those who journey here are first met with a mass of stone. Moving through the Border allows a traveler to find caverns and tunnels until the Border abruptly jettisons a traveler out into the demiplane. Following these tunnels and moving deeper into the plane, the rocks give way until explorers see bridges extending out into a void, at the very ends of these bridges, the rocks are crumbling away and slowly circling down into a black abyss far below. It is said that space and time are heavily distorted in this demiplane and that staying here too long can cause years to pass outside. No one knows what is in the abyss, and no one has ever returned.