Part the First: The Psycotropic Mists

The common opinion of the Ethereal Plane is that it is a misty realm filled with protomatter, relatively unchanging, and not hazardous in and of itself. However, the common opinion is wrong. The mists of the Ether are far more than what they seem at first glance. Far from being unchanging, the mists are actually psychotropic; that is, they change according to what those near them are thinking. Two factors affect how much the mists change: how strong a mind is changing them, and the proximity of the mind or minds doing the changing. The mind or minds that affect the mists do not need to be aware of the fact they can do so, although awareness does make it easier to change them.

Why then, does most of the Ethereal Plane take the form of a very large fogbank? The reason the Border Ethereal is so formed is that when people first travelled through the Ethereal, there was almost no Border Ethereal. No one knew about it, so it did not exist in a noticeable form. The planewalkers came upon the Deep Ethereal, which was even then in the form known today, and reported the Ethereal as such to everyone when they returned. Thus, everyone believed the Ethereal to be a fog of protomatter, and the Border Ethereals took on that form. But this begs the question of why the Deep Ethereal is in its current form. Experiments have proved that powerful minds can bend the Deep Ethereal to their will, but only in a small area and for a short time, before it reverts to its usual form. The most logical explanation for this is that somewhere in the Deep Ethereal lies an enormously powerful mind that is forcing the Deep Ethereal to take on a form of its own devising. What this mind's goals are, or when it first came into existence, are secrets to which no one knows the answer.

But the Border Ethereals, perhaps because of their relative closeness of the Prime Material Planes, are less affected by whatever it is that shapes the Deep. Because of this, they are far more mutable. In fact, sometimes beings with strong wills accidentally cause the mists to form things. This is especially prevalent in psionicists and wizards, who are used to shaping the world through the power of their minds. Such unconscious shapings can take many forms. Sometimes the creator shapes the thing he or she most desires. Other times, the creator's worst enemy can form, or their greatest fear (1). The Ethereal Plane can also be shaped deliberately, by those knowledgeable of the properties of the Ethereal Plane.

Part the Second: Non-standard Ethereal Planes

The Border Ethereal Plane is not always the same as the Deep Ethereal Plane. On some worlds, cultures believe in things and creatures that do not truly exist anywhere. If enough people believe in such things strongly enough, the Ethereal can begin to take on the shape of that belief.

A good example of this is the belief many primitive cultures have regarding the spirits and the spirit world. Many shamans in these cultures claim to be able to enter the world of the spirits, travelling in spirit themselves. There, they deal with a supernatural mirror of the world, talking to the spirits of the animals, plants, and natural features. And clearly these things have power, for the shamans can cast spells. But where are these spirit worlds? The obvious answer would be in the Outer Planes. But the description of the spirit world does not agree with any known Outer Plane. The Beastlands, and the Plane of Cordance Pangea, would seem to be good candidates, but the spirit world is usually described as changeable and somewhat insubstantial. Furthermore, even the most inexperienced shaman can often go into the spirit world. The ability to plane travel from the prime material to the Outer Planes does not seem possible for such weak people, even in spirit.

The next obvious answer would be that the spirit world is some form of demiplane. Indeed, a few spirit worlds do seem to be just that. Yet there are thousands of cultures that believe in spirit worlds. Surely if all of them were demiplanes, more portals would lead to them from the other planes, and spirit animals would roam the streets of Sigil. And, again, the difficulty of the ability of even weak and inexperienced shaman to travel to the spirit world comes up.

What does this leave us? The Astral is too barren. The Inner Planes nature is well established, and it is not the spirit world. The theoretical Ordial Plane might be it, but that presents an even greater distance to travel, planewise. This leaves the Ethereal. And, indeed, experiments have proved that the Border Ethereal can take the form of a spirit world. A mage went to a world where belief in the spirit world was very common, and cast a spell to bring herself into the Border Ethereal. Instead of the usually misty plane, she found a thriving landscape, populated by spirit animals. The belief of the people had shaped the Ethereal.

A more sinister aspect of this shaping by belief could have resulted in the creation of the rumoured Demiplane of Dread, Ravenloft. The concept is that on one prime world, several people had bad experiences travelling through the Ethereal, bringing their darkest fears to life. They escaped, and told others what had happened. This fostered a belief that the Ethereal was a dangerous place, where terrible beings lurked. This, in turn, make it more likely that people's fears would form out of the plane, reinforcing the tales of danger, and so on in a deadly cycle. Eventually, the Border Ethereal around this prime material became so horrible, so filled with the creatures of nightmare and dark legend, that it overran the prime it surrounded, and took on a life of its own, its nature supported by those who lived in it, who of course believed wholeheartedly in its monstrous evil. Although this is speculation, research into the Ethereal seems to bear out this theory. Further examination will tell.

Part the Third: An Examination of Ethereal Cultures

Sometimes, the prime material is not the primary shaper of the Ethereal. If people discover the true nature of the Ethereal, they often move there, forming living space by the force of their minds. If enough people move into the Ethereal, whole societies can form. Usually, these societies form living spaces, tailored to their tastes, out of the mists of the Border Ethereal. These dwellings, while separated from the mists of the Ethereal, usually by solid borders, are still part of the Ethereal Plane, and not separate demiplanes.

As time goes on, and societies separate into new groups, new dwellings are formed. Eventually, as many societies form and grow, a sphere of dwellings is formed, one being piled on top of, or beside, or beneath, others. As societies move outward, the inner core areas can become deserted, scorned as the residences of backward, decadent cultures.

This can give rise to areas of wilderness, haunted by dark creatures created by evil beings out of the mists. Over thousands of years, the Border Ethereal can become a more complex world than the Prime Material that spawned it.

Another form of Ethereal culture that can form is one that does not know of the properties of the Ethereal, simply treating their home as a parallel world, to the Prime, and moving back and forth when it suits them. Such a culture is often ascribed to the Sidhe, elflike beings that worship the Celtic Pantheon, and compete with their mortal worshippers. In most stories, when the Celts moved into lands they now held, they forced the Sidhe out. Some Sidhe moved away to other lands, but others took up residence in a parallel world, called, variously, Faerie, Elfland, and Underhill. This place could easily be an Ethereal domain, formed out of the belief of the humans and the desire of the Sidhe for a home.

-- The Sage of Everything

Footnotes:

1. There is a 0.1% (a result of 001, rolling 3d10) chance per trip of a psionicist or wizard unconsciously shaping the Ethereal, in Border Ethereals that are standard. The DM should create a suitable encounter. If the DM cannot think of a suitable nightmare for the player to face, a Feyr, from the Monstrous Manual, can be used. Remember, however, that a greatest fear should be more powerful than the character alone. Otherwise it would not be something to be afraid of.