The Ethereal plane is a plane of swirling proto-matter coexisting alongside Prime Material plane, touching the Prime at all points. The Ethereal is the cosmic “glue” that binds together the Prime Material and inner planes. It also contains the stuff that new demi-planes are made of. It is a roiling, chaotic plane filled with swirling fogs and shadowy shapes in various degrees of solidity. Travelers and the few natives that exist in this plane appear semi-solid as well, and nonliving objects can pass through each other easily.
The first-time visitor deep within the plane may find himself completely surrounded by colorful mists, or in areas that resemble small towns on misty, fog-bound evenings. There is gravity in the sense of an up and a down direction, but the ethereal visitor can move in all directions freely. Visitors and other objects are supported by the ethereal medium, so that unsupported objects do not fall in Ethereal plane, despite the existence of a down direction. The traveler in the Ethereal consists of the same base material, and therefore has the same density, as his surroundings. A traveler can move forward, backward, up, or down by parting the vaporous medium at will.
The Ethereal is unique among the planes in that a visitor can exist simultaneously in both the Ethereal and another plane, in a region of the Ethereal plane known as the Border Ethereal. The Border Ethereal is explained below and is considered part of the Ethereal plane (the “edge” of the infinite plane). The non-Border parts of the Ethereal are referred to as the Deep Ethereal. The Ethereal can be thought of as a great ocean, so that a traveler can wade along the beach (in the Border Ethereal), alongside familiar lands, or journey across the Ethereal Ocean (the Deep Ethereal) into new lands.
The Ethereal plane is used as a means of travel from the Prime to the inner planes, which include the elemental, para-elemental, and quasi-elemental planes, as well as the Positive and Negative Material planes. The Ethereal also provides access to the demiplanes.
The Ethereal plane (and the realms beyond it) can be most easily reached via magical items, such as oil of etherealness or armor of etherealness. These and similar magical items place the user and those items he carries into the Border Ethereal, that place where the Prime and Ethereal meet.
A traveler becoming ethereal slowly disappears from view, taking a round to fade away, whether entering the Deep Ethereal or the Border Ethereal. The ethereal traveler is invisible for as long he remains in the Ethereal plane; when he leaves the Ethereal plane, he rematerializes in one round in the next plane on his itinerary. A traveler returning from the Ethereal plane can take actions and attack others in the Prime plane but cannot disappear again into the Ethereal until the following round. The most common example of this are creatures with phasing abilities such as phase spiders. They reappear and deliver their deadly bites in one round but require the next round to return to their invisible and ethereal state.
The Ethereal plane is accessible at every point of the Prime Material plane it touches, so there are no free-standing ducts, gates, or portals. Rather, the entire Prime is bordered by the Ethereal; those who walk along this border can interact with creatures on the Prime plane. To use the analogy of the Ethereal as an ocean, a person in the Border Ethereal is standing in the surf of that ocean where it meets the shore. He can see what is happening on the shore, and he can move along the shore, but he is still in the water. Thus a traveler standing in the Border Ethereal can see into the Prime plane, but he is still an ethereal being. Subjective time flows for the traveler in the Border Ethereal as for the plane he is viewing. In the Border Ethereal with the Prime Material and outer planes, subjective time flows at the same rate as true time.
An individual in the Border Ethereal is invisible to those in the bordering plane, although he can be detected from that plane by means of the defect etherealness or detect invisible spells. Such a traveler revealed would appear as a smoky, translucent shade. Travelers in the Border Ethereal are visible to others in the Border Ethereal. Individuals in the Border Ethereal cannot verbally communicate with inhabitants of the plane they border, nor can they use equipment, items, or spells to attack individuals in the plane they border. Likewise, inhabitants of the other plane cannot attack beings that are in the Border Ethereal. Certain spells, such as phase door and dispel magic, can bring the beings out of the Border Ethereal and into the other plane.
Border Ethereal creatures can attack each other, and they can be attacked by creatures that have attacks capable of reaching into the Ethereal plane. Travelers in the Border Ethereal can move through the plane they are bordering without problem, moving vertically or horizontally at will without need for support. They travel at the speed they would move on that plane given their usual movement abilities. The traveler in the Border Ethereal can move through solid matter in the plane he borders without ill effects in most cases. Stone can be breached without creating an opening, and the ethereal traveler can pass through a wall of fire or volcano unscathed, provided it is on the other plane. Damage that extends into the Ethereal plane does affect the ethereal traveler.
The dangers of invisible individuals walking through walls via the Border Ethereal have not been lost on the powers that live in the planes adjacent to it. Three things in the plane bordering the Ethereal hinder movement in the Ethereal: certain spells that detect and ban the ethereal, dense metals, and living beings.
Spells can effect creatures in the Ethereal. An alchemic mixture containing gorgon’s blood that, when mixed with the mortar of a building, prevents ethereal and astral creatures from passing through the walls. This last potion usually costs 10,000 g.p. from a reputable alchemist.
Dense metals also prevent passage by those in the Border Ethereal, so a large collection of gold or plates of lead can be used to ethereal-proof an area. Any metal denser than gold can be used, though this is often an expensive proposition. This method also allows dwarven and human miners to discover new veins of dense ore by sending scouts in the Border Ethereal through the surface. The type of material found cannot be determined in this fashion, however, and unlucky miners may dig up an ancient, sealed tomb of a fell power.
Living beings (at least those above the one-celled level) generate an aura that prevents passage by ethereal beings. Thus a guard outside the door of a room whose walls were built with gorgon’s blood in the mortar prevents ethereal passage. This aura radiates about a foot in all directions, so that it is possible to pass under or over living guards. Because of this aura, a traveler cannot materialize partially inside the body of an opponent, or leave a weapon where it will rematerialize into a living creature. Plants also radiate this aura, so a vine-covered cottage is also immune to ethereal visitors.
A traveler in the Border Ethereal sometimes may be forced to regain his physical form inside an existing object. (This usually occurs because the spell or potion has expired or a dispel magic has been cast upon the traveler.) Liquids, gases, and flames part to allow the traveler entrance, but solid objects resist such intrusions. A traveler reappearing inside a solid object must roll a saving throw vs. death magic. Failing that save results in the physical destruction of the traveler; success plunges the traveler into the Deep Ethereal, where he is unconscious for 1d4 true rounds. Several travelers reappearing together are sent to different areas of the plane. Those who survive the trauma remain ethereal until they choose to enter another Border Ethereal, at which point they become non-ethereal and emerge into the plane they have chosen.