The Plane of Shadow

It is the toxic plane of darkness and power.
It is the hidden place that hates the light.
The Plane of Shadow is a darkly lighted dimension that is both coterminous to and coexistent with the Material Plane. It overlaps the Material Plane much as the Ethereal Plane does, so a planar traveler can use the Plane of Shadow to cover great distances quickly. The Plane of Shadow is a world of black and white; color itself has been bleached from the environment. It is otherwise appears similar (but not exactly identical) to the Material Plane. The sky above, for example, is always a black vault with neither sun nor stars. Landmarks from the Material Plane are recognizable on the Plane of Shadow, but they are twisted, warped things—diminished reflections of what can be found on the Material Plane. Despite the lack of light sources, various plants, animals, and humanoids call the Plane of Shadow home. The Plane of Shadow is highly morphic, and parts continually flow onto other planes. As a result, precise maps are next to useless, despite the presence of land-marks. If a traveler visits a mountain range during one use of a shadow walk spell, the mountain range may still be there the next time, but the individual mountains may have moved about. Precision is a lost cause in the Plane of Shadow. The terrain of the Plane of Shadow is usually similar to the area where the traveler enters from the Material Plane. If a wizard travels onto the Plane of Shadow from a forest, she first sees an equivalent shadow forest. If she starts underwater, she appears within a shadowy sea that behaves like a Material Plane ocean, so her water breathing spell still works. However, as she moves away from her entry point, the terrain of the Plane of Shadow changes dramatically, although it usually bears some resemblance to the corresponding terrain on the Material Plane. Spells often draw forth parts of the Plane of Shadow, in particular for illusions that have the shadow descriptor. The Plane of Shadow is a monochromatic world, but shadow material pulled from it can be of any color. The spellcaster usually colors, shapes, and shades the shadowstuff to make it more convincing. A shadow evocation that produces a fireball, for example, appears like any other fireball to those fooled by the illusion.
The Plane of Shadow is up in the metaphysical sense from the Material Plane and lies further from the Physical Planes. It is in essence the metaphysical shadow cast by the Material Plane in the flow of elements and energies from the Physical Planes.

Movement in the Plane of Shadow

Movement is as normal on the Plane of Shadow, but travelers can cover great distances on the corresponding Material Plane by stepping across the Plane of Shadow. Those who know the way can access other planes from the Plane of Shadow. Thrill-seekers can simply wander through the Plane of Shadow, looking for adventure.
Most Material Plane creatures on the Plane of Shadow use the shadow walk spell. With this spell, the caster moves into the Plane of Shadow, moves in a particular direction for a certain amount of time, and then steps back into the Material Plane. Cardinal directions (north, south, east, and west) are the same on the Plane of Shadow and the Material Plane, but distances are deceptive. Travelers simply move faster on the Plane of Shadow than on the Material Plane. For every 10 minutes moving in a particular direction, someone using shadow walk covers seven miles in the same direction on the Material Plane. The travel speed is the same regardless of the speed of the creature using shadow walk. Whether a wizard is mounted, on foot, or flying, she covers the same distance in the same time. To maintain the pace, the traveler need only keep moving.
Once the creature using shadow walk reaches the desired location, the second part of the spell activates. This opens a portal back onto the Material Plane, again with a shadowy road leading there. This road is illusory, but the portal at the end is real. The traveler emerges among the nearest shadows to the destination. By studying the surroundings on the Plane of Shadow before emerging, a traveler may have some idea of where she is going to appear. When moving through the Plane of Shadow, travelers see shadowy landscapes that are similar to, though not exactly alike, the corresponding terrain on the Material Plane. Rivers may be changed or absent, for example, and castles present, ruined, or altered entirely. But the basic terrain type (marsh, hills, and mountains) remains the same.
A traveler can force herself out of the areas that correspond to the Material Plane, however. In this case terrain grows extreme: Trees are more massive than anything on the Material Plane, mountains become cliff-like barriers, and rivers are raging torrents. In this rough terrain, shadow travelers find portals that move through the Astral Plane and onto the Spiritual Planes. It takes 1d4 hours of constant travel to find a random portal of this type. When opening the portal at either end with a shadow walk spell, the traveler creates a weak spot between the Material Plane and the Plane of Shadow. This weak spot lasts 1d6 × 10 minutes. During that time, creatures on the Plane of Shadow may attempt to push their way onto the Material Plane—or vice versa. It takes a Will saving throw (DC 15) to push through to the other side, and the attempt can be made only once per weak spot.
Individuals lost, abandoned, or otherwise stranded on the Plane of Shadow must locate such a weak spot in the shadowy fabric of the plane, happen across a permanent portal or natural vortex, or find a traveler willing to bring them back to the Material Plane.

Creatures of the Plane of Shadow

While the Plane of Shadow is not evil in and of itself, it is home to a wide variety of foul creatures that hate the light and the living. The best known denizen of the plane is the shadow, an undead creature that sucks the strength from adventurers on either the Material Plane or the Plane of Shadow. The Plane of Shadow has native versions of many of the plants and animals found on the Material Plane, but the shadow versions are twisted, dark variants. More dangerous monsters such as the shadow mastiff and the nightshade call the Plane of Shadow home as well.
There are numerous stories of castles and entire cities that have been sucked up by the Plane of Shadow over the years. Some still survive, but they have been warped by the insidious, toxic nature of the Plane of Shadow. This toxicity, described in the Features of the Plane of Shadow section below, only manifests after decades on the Plane of Shadow. It grants strange abilities and inhuman attributes to those infected by shadow's touch.

Locations and Features of the Plane of Shadow

Dark Mirages

One of the most distressing features of the Plane of Shadow is that it is a warped reflection of the Material Plane. A shadow traveler who enters the Plane of Shadow from her hometown may find herself in a dark, abandoned version of that town. The parallels are not exact, so her home may be on a different street, be built in a different style, or (most likely) lie in ruins. Other mirages are equally troubling, such as a huge dark castle where none exists on the Material Plane, or an ancient battlefield where a dungeon should be. Most troubling of all are the shadowy echoes of people the traveler knows, shadow creatures with the twisted but still recognizable features of loved ones. These shadow duplicates have no special abilities, but the effect is disconcerting nonetheless.
Shadow travelers in a place particularly familiar or meaningful to them must make a Will saving throw (DC 15) to ignore such dark mirages. Those who fail are haunted and rattled by the similarities, suffering a –2 morale penalty on attacks and saving throws as long as they remain in a location familiar to them. Travelers who make their saves are unaffected by the dark mirages for the duration of their trip to the Plane of Shadow. Dark mirages occur because the Plane of Shadow is so close to the Material Plane.
Oracles and soothsayers sometimes journey onto the Plane of Shadow looking for enlightenment among the darkness, attempting to discover if such dark mirages are harbingers of the future.

Darklands

On the Plane of Shadow, patches of darkness exist that are even darker than the shadows themselves. Negative energy infuses these places. Whether the negative energy is bleeding over from the Negative Energy plane or it's simply a byproduct of the high concentration of undead shadows and other life-draining undead is unknown. Darklands regions have the minor negative-dominant trait. Living creatures that enter the darklands take 1d6 points of damage per round from negative energy and crumble into ash if they reach 0 hit points or less. Spells and magic items that protect against negative energy function normally within the darklands.
Travelers to the Plane of Shadow can identify darklands easily. They are more desolate and bleak than the surrounding areas (which are themselves pretty bleak on this plane). Plants are dead and desiccated from the long-term effects of the negative energy. Natural vortices from other planes do not open into darklands regions, and spells or spell-like abilities opening a portal from the Material Plane warn the traveler (usually with a cold shiver down the spine) that a darklands region lies ahead. Darklands often correspond to haunted battlefields, unconsecrated graveyards, and lairs of powerful necromancers on the Material Plane, as well as any location dominated by undead.

Astral Portals

The Astral Plane is coterminous to the Plane of Shadow, so magic portals can create conduits through the Astral Plane to anywhere the Astral Plane touches. Such portals are found in the rougher regions far from the “normal” areas of the Plane of Shadow. A traveler who can't reach the Outer Planes directly can travel to the Plane of Shadow and find a portal that uses the Astral Plane to reach her destination.

Shadow Quakes

The Plane of Shadow is a morphic landscape, but in general it moves slowly. Over the course of a week the landscape may alter sufficiently to be unrecognizable, although someone continually observing the plane wouldn't see it actually moving. But the Plane of Shadow has its own version of earthquakes that can prove deadly to the shadow traveler.
Shadow quakes tend to be dramatic but localized, having the same effect as an earthquake spell within a 100-foot radius. Flying and incorporeal creatures are unaffected. The shadow quake can also break the effect of a shadow walk spell. The spellcaster must make a Concentration check (DC 20) to maintain control of the spell. If the caster fails, the spell's targets are stranded on the plane as if lost or abandoned. It is still possible to return to the Material Plane by casting another shadow walk or locating a shadow vortex or other portal.

Traits

Normal Gravity.
Normal Time.
Infinite Size.
Magically Morphic: Spells such as shadow conjuration and shadow evocation modify the base material of the Plane of Shadow. The utility and power of these spells within the Plane of Shadow make them particularly useful for explorers and natives alike.
No Elemental or Energy Traits: Some small regions on the Plane of Shadow have the minor negative-dominant trait, however.
Mildly Neutral-Aligned.
Enhanced Magic: Spells with the shadow descriptor are enhanced on the Plane of Shadow. Such spells are cast as though they were prepared with the Maximize Spell feat, though they don’t require the higher spell slots.
Furthermore, specific spells become more powerful on the Plane of Shadow. Shadow conjuration and shadow evocation spells are 30% as powerful as the conjurations and evocations they mimic (as opposed to 20%). Greater shadow conjuration and greater shadow evocation are 60% as powerful (not 40%), and a shade spell conjures at 90% of the power of the original (not 60%). To calculate the effect of such spells, take advantage of Maximize Spell to garner maximum hit points or maximum damage, then apply the percentage above.
Impeded Magic: Spells that use or generate light or fire may fizzle when cast on the Plane of Shadow. A spellcaster attempting a spell with the light or fire descriptor must succeed at a Spellcraft check (DC 15 + the level of the spell). Spells that produce light are less effective in general, because all light sources have their ranges halved on the Plane of Shadow. Despite the dark nature of the Plane of Shadow, spells that produce, use, or manipulate darkness itself are unaffected by the plane.