The Ethereal Plane

It is a plane out of phase.
It is a place of ghosts and monsters.
It is right next to you, and you don't even see it.
The Ethereal Plane is a misty, fog-bound dimension that is coexistent with the Material Plane. 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 Plane is down in the metaphysical sense from the Material Plane and lies closer to the Physical Planes. It is made up out of protomatter created by the mixing of the elements and energies that flow up towards the Material Plane and acts as a metaphysical screen protecting the Material Plane from the unbridled power of the Physical Planes.

Movement in the Ethereal Plane

One moves through the Ethereal Plane as one would move on the Material Plane. However, due to the misty nature of the protomatter of the plane itself, a traveler can move up and down just as easily as along solid surfaces. However, all movement is at half speed, both for travelers and for creatures native to the Ethereal Plane. There is a definite “down” to the Ethereal Plane that corresponds to the gravity of the coexistent plane it is attached to. However, there is no danger of falling. Because the Ethereal Plane is coexistent with the Material Plane, most travelers walk normally along the ground of the Material Plane. Creatures on the Ethereal Plane can move through solid objects on the Material Plane, but they cannot move through solid objects on the Ethereal Plane. Unlike the Astral Plane, the Ethereal Plane offers no quick way to move great distances. A traveler normally moves physically between the Material Plane and the Ethereal Plane, unlike travelers to the Astral Plane, who sometimes project a duplicate form. The most common way to reach the Ethereal Plane is with spells such as ethereal jaunt or magic items such as armor with the etherealness special ability. There is no inherent danger when moving from the Material Plane to the mostly empty Ethereal Plane. Even if there is an ethereal object in the way, the traveler is painlessly shunted to the nearest open space in the Ethereal Plane.
Moving back to the Material Plane poses a risk if a solid object or creature is present. Travelers who overlap with a Material Plane object or creature are shunted to the nearest open space, taking 1d6 points of damage per 5 feet so moved.

Creatures of the Ethereal Plane

The Ethereal Plane is much more populated than, for example, the Astral Plane. It boasts a great variety of natives as well as frequent travelers. Magical beasts such as the ethereal marauder, phase spider, and ethereal filcher use the Ethereal Plane. These are not true outsiders, but rather Material Plane creatures that have adapted to use the Ethereal plane to hunt prey. Travelers to the Ethereal Plane include outsiders that have access to magic portals. As stated above, moving onto the Ethereal Plane by means of a gate or plane shift spell turns the traveler ethereal. It takes a second spell to return travelers to their plane of origin.
One great danger of the Ethereal Plane is ghosts, which often call this plane home. Such creatures have a deep and abiding hatred of the living, and no love for those travelers who impinge upon their realms.

Locations and Features of the Ethereal Plane

Ethereal Solids

In general, movement on the Ethereal Plane is unrestrained. Travelers can journey to the center of the earth or high into the sky (though slowly and limited by available food and water). There are, however, permanent objects on the Ethereal Plane that can block movement for ethereal creatures. Ethereal solids are hard to the touch and feel real, even if they have no apparent reality on the coexistent Material Plane. Often these ethereal solids are the result of activities in the coexistent Material Plane. There are several types of ethereal solid.
Force: Force effects extend onto the Ethereal Plane and affect the creatures therein. A wall of force, for example, prevents an ethereal creature from passing through it. In general, an ethereal traveler sees what a Material Plane native would see. Depending on the spell, this might be nothing at all.
Ethereal Objects: These objects have been constructed on the Material Plane, then shunted (usually magically) to the Ethereal Plane. A chest of valuables can be sent onto the Ethereal Plane with a vanish spell, for example, or a creature might have been turned to ethereal stone by a medusa's gaze.
Larger objects exist on the Ethereal Plane, too. For example, a wizard might seek privacy from extraplanar interlopers in her personal library. She turns a 20-footby-20-foot slab of stone ethereal, then builds her Material Plane library on the spot coexistent with the slab. Or, through a deity's favor, a powerful baron moves an entire mountain onto the Ethereal Plane and builds his keep where the mountain used to be. Ethereal intruders encounter a stone block in the first case and a mountain in the second-both impassable objects for would-be spies. An ethereal object, if forced to manifest on the Material Plane, cannot reappear where it had vanished from if another object occupies that space; if so, it is displaced to the nearest area that can hold it. In the second example above, the mountain does not reappear in the space the keep occupies. As long as the keep is taller than it is wide, the mountain is shunted to the side if forced to appear on the Material Plane. But if the shortest direction for the mountain to reappear is straight up, then the baron has a new problem.
Dead Magic Areas: A traveler using magic to reach the Ethereal Plane cannot move into an area with the dead magic trait without returning to the Material Plane. On the ethereal landscape, dead magic areas appear as massive black blots.

Ether Cyclones

Akin to the psychic storms of the Astral Plane, ether cyclones are pressure centers of magical force that roil through the Ethereal Plane. They brew up out of nowhere and pose a hazard to ethereal travelers in the area. They are usually as temporary as thunderstorms on the Material Plane, but sometimes a more permanent ether cyclone can develop, lasting for years or even centuries. To those on the Material Plane, the ether cyclone has no effect beyond a shiver down one's spine or strange behavior from nearby animals. But on the Ethereal Plane, the ether cyclone is an incredibly strong wind. Clothing, hair, and unattended objects are blown about, and eventually a traveler is uprooted and spun through the Ethereal Plane to an unknown fate. The rising winds of a typical ether cyclone provide 1d10 rounds of warning before the cyclone reaches full strength. An eerie howling increases with each round, and with a brutal suddenness the ether cyclone tears at everything in its path. Travelers can flee the ether cyclone by moving onto the coexistent plane or seeking shelter. Spells with the force descriptor, such as Leomund's tiny hut, protect the traveler from the effects of an ether cyclone, but weather spells such as control wind and control weather have no effect on an ether cyclone. It's otherwise impossible to outrun an ether cyclone. One of the greatest dangers of an ether cyclone is how it can scatter a group of adventurers, leaving them unable to find each other—or to find exits from the Ethereal Plane. At the DM's option, roll only once on the table below for a group of travelers, provided they are relatively close to each other when the ether cyclone strikes.
Undead are unaffected by ether cyclones, including ghosts and such creatures as devourers. Ghosts that aren't tied to a particular Material Plane location may even ride an ether cyclone, surfing on the ethereal winds.
Any creature becoming ethereal (including those who use the blink spell) in an ether cyclone immediately suffers the effects of the cyclone. But creatures about to move to the Ethereal Plane get a feeling that there is something unusual on the other side if an ether cyclone is nearby. They may choose not to enter the Ethereal Plane as a result.

d%	Effect
01-30	Take 1d10 points of damage (Fort save DC 20 negates). Roll again in 1 minute if still within the cyclone.
31-60	Move 1d10 miles in a random direction. You are no longer in the storm and can move back normally.
61-80	As above, but 2d20 miles in a random direction.
81-90	As above, and take 3d10 points of damage (Fort save DC 20 negates).
91-100	Take 3d10 points of damage (Fort save DC 20 negates) and return to the Material Plane. If you reappear inside a solid object, you’re shunted aside but take 1d6 points of damage for each 5 feet traveled this way.

Traits

No Gravity.
Normal Time.
Infinite Size.
Alterable Morphic: There is little on the plane to alter, however.
No Elemental or Energy Traits.
Mildly Neutral-Aligned.
Normal Magic: That is, spells function normally on the Ethereal Plane, though they do not cross into the Material Plane. It is possible to use a fireball spell against an enemy on the Ethereal Plane with the caster, but the same fireball wouldn't affect anyone on the corresponding part of the Material Plane. A bystander on the Material Plane can walk through an ethereal battlefield without feeling more than the hair on the back of his neck standing up.
The only exceptions are spells and spell-like abilities that use magical force (noted with the force descriptor, such as magic missile or wall of force) and abjurations that affect ethereal beings. Spellcasters on the Material Plane must have some way to detect foes on the Ethereal Plane before targeting them with force-based spells, of course. While it's possible to hit ethereal enemies with a magic missile spell cast from the Material Plane, the reverse isn't possible. No magical attacks cross from the Ethereal Plane to the Material Plane, including force attacks.