The Ethereal Plane

The Ethereal Plane is a misty, fog-bound dimension that is coexistent with the Material Plane and often other planes as well. Travelers within the Ethereal Plane describe the plane as a collection of swirling mists and colorful fogs. The Material Plane itself is visible from the Ethereal Plane, but it appears muted and indistinct, its colors blurring into each other and its edges turning fuzzy. Ethereal denizens watch the Material Plane as though viewing it through distorted and frosted glass. While it is possible to see into the Material Plane from the Ethereal Plane, the Ethereal Plane is usually invisible to those on the Material Plane. Normally, creatures on the Ethereal Plane cannot attack creatures on the Material Plane, and vice versa. A traveler on the Ethereal Plane is invisible, incorporeal, and utterly silent to someone on the Material Plane. This makes the Ethereal Plane very useful for reconnaissance, spying on opponents, and other occasions when it's handy to move around without being detected.
The Ethereal plane is mostly empty of structures and impediments. However, the plane has its own inhabitants. Some of these are other ethereal travelers, but the ghosts found here pose a particular peril to those who walk the fog.
The Ethereal touched the prime material plane at all points, coexisting at all points in space, like a shadow or reflection of the plane. This deep mist of ghosts and spirits extended beyond the material plane and infinitely outward, and could be found like mist against glass on the borders of the Crystal sphere, known as the Border Ethereal. When a traveller crossed into the Border Ethereal, she and all her possessions were converted to their Ethereal equivalents, metal became ethereal metal, flesh became ethereal flesh and so on, allowing free movement (in most cases) in any direction through the solid matter of the adjacent plane. Since everything was permeated with ethereality, an air-breathing creature could breathe ethereal air and could not drown in an ethereal lake nor be crushed by an ethereal rock. The non-border region was called the deep ethereal, a powerful arcane landscape of energy and power. These regions swirled with large areas of protomatter, which could form a demiplane when a critical size was reached. Powerful wizards, sorcerers or demigods could bend this proto-matter to their will and create a demi-plane, some of which could exhibit their own rules of gravity and physics, or even support life. The largest of these planes are the positive and negative mirror realities of the prime material plane, known as the feywilds and shadowfell, though most demiplanes eventually collapse into themselves, break up or merge into the prime material plane.
One could enter the ethereal plane through spells such as etherealness, or through other magical means. All mortals live in both the material and ethereal plane at once, their souls occupying the space in the ethereal that their physical body does in the material. One's connection between these two states is broken when one dies, and souls which are not claimed by a deity upon death remain in the ethereal plane as spirits and ghosts. The connection can also be artificially broken by creatures such as phase spiders, or particularly powerful enchanted weapons. Vengeful spirits often linger in this space, refusing to pass on to an outer plane, and haunt individuals or places upon the material plane.
There is no direct danger to general survival on the Ethereal Plane. The Ethereal Plane has a normal atmosphere, and inhabitants breathe normally. Inhaled poisons and spells such as cloudkill work on the Ethereal Plane. However, there is no food or water other than what travelers bring with them. Someone trapped on the Ethereal Plane without a way out risks eventual starvation or dehydration.
Unlike most planes, the Ethereal Plane allows vision across the planar border to the plane it's coexistent with: the Material Plane. No matter where you are on the Ethereal Plane, you can see the corresponding part of the Material Plane. Vision is limited, however, to 60 feet both on the Ethereal Plane and onto the Material Plane.
Furthermore, the Material Plane appears as if wrapped in fog, so ethereal observers can't discern precise details such as normal writing. It's easy to discern faces and landmarks, however. Seeing and hearing is otherwise normal, so gaze attacks and sonic attacks and abilities launched from the Material Plane affect ethereal creatures.
The reverse isn't true. An ethereal traveler is normally invisible and inaudible to an individual on the Material Plane. Spells and abilities such as see invisible reveal an ethereal object or creature
Creatures on the Ethereal Plane cannot talk to those on the Material Plane, even if they want to be heard. Ethereal listeners only hear Material Plane sounds that originate up to 60 feet away, but their hearing is otherwise unaffected. Touch, smell, and taste do not reach between the planes.
The Ethereal plane emits its own diffuse light, so ethereal observers do not need torches to see onto the Material Plane, even if it's pitch-black. Light sources do not expand the 60-foot vision limit on the Ethereal Plane, nor do alternate methods of sight such as darkvision. Blindsight used on the Material Plane does not reveal Ethereal Plane creatures, but a creature with blindsight on the Ethereal Plane can detect other ethereal creatures at its normal range.
To viewers on the Ethereal Plane, objects on the Material Plane are foggy, indistinct, and almost translucent. Such objects block line of sight and provide concealment, but not cover. An ethereal observer can't see through a wall on the Material Plane unless he pokes his head through it first.
An ethereal character whose eyes are totally within a Material plane object cannot see.

Known Demiplanes

• The Feywilds
• Shadowfell
• The Fugue Plane
• The Black Abyss
• Demiplane of Moil
• The Mazes
• The Realm of Dreams
• Neth, the Demiplane that Lives