Shadowstuff, or shadow substance, was a shadowy form of matter integral to the Plane of Shadow. It was found in items and phenomena there and in the bodies of creatures of darkness, and it was employed in some forms of illusion magic and shadow magic. It could also be crafted as weaponry, building materials, and other items, but such things were hazy, insubstantial, and all too impermanent. Shadowstuff merged with rock was known asshadowstone.

Locations
Shadowstuff was found on the Plane of Shadow. It was part of the fabric of the plane itself.The morphic nature of the Shadow Plane caused shadowstuff to manifest in strange ways. For example, in a cave in the Black Rift in the Shadow Swamp, stalactites dripped ephemeral shadowstuff, which was reabsorbed into the plane rather than form a puddle.

Sites in the Shadow Fringe, the intersection between the Shadow Plane and the Prime Material Plane, tendrils of shadowstuff appeared and were seen to ebb and flow like tides. This was the case in the Underdark city ofChaulssin, the City of Wyrmshadows.

Curiously, the darkberry bush that grew in forests all around the Inner Sea on Toril in the Material Plane produced small, purple berries that contained shadowstuff. When crushed, they released a globe of darkness one could briefly hide in.

Creatures
The aberrant creatures known as cloakers, which had the power to manipulate shadow, appeared to have a special affinity with shadowstuff. When multiple cloaker lords governed a community, they would periodically come together in a Conclave of Shadows, grasping claws and arranging themselves in certain orientations to collectively form a ring, or occasionally a sphere. The whole conclave would then transform into a ring or sphere of living shadowstuff, with their minds merged. This was a temporary merger; when a matter was decided, the cloaker lords would separate as individual beings again.

The shade archmages of Thultanthar, the City of Shade, tended to be infused with shadowstuff and wielded its power.

A dark creature, one with a very strong connection to the Plane of Shadow, weighed somewhat less than an equivalent creature, suggesting a portion of its very substance had been replaced by shadowstuff. Dark creatures possessed a supernatural ability to hide in darkness and other powers, and had a duller coloration.

A shadowslain creature was shrouded in shadowstuff, which formed a semisolid armor that deflected blows and helped it conceal itself.

Uniquely, the black dragon Despayr, who was unable to breathe acid as others of his kind did, learned to breathe shadowstuff instead. This took the form of a barrage of shadow shards.

Usage
The cloaker city of Rringlor Noroth in the Underdark traded heavily in shadowstuff items. The Shadowstalkercaste hunted on the Plane of Shadow where they gathered raw shadowstuff and carried it home. The Shadowweaver caste then fashioned the raw shadowstuff into lasting goods, for their own use and a small quantity for trade with other races. Although they typically dissipated within a tenday of sale outside the city, many came to Rringlor Noroth for shadowstuff items and weaponry.

Shadowstuff could even be used as a construction material. For example, Rringlor Noroth was carved into an arching bridge of shadowstuff stone called the Shadowspan, which spanned the Rift of Dhalnadar and lay in both the Material Plane and the Demiplane of Shadow. This “shadowstuff stone”or “shadowstone” was the result of rock and shadow substance existing where the two planes existed conterminously—that is, in exactly the same location with exactly the same boundaries. The bridge was only semi-solid, apt to dissolve and become immaterial at random places, if not continually subjected to certain subsonic moans delivered by the Orbmantlecaste of cloakers.

Meanwhile, buildings in the Shadow District of the Underdark gloaming city of Sphur Upra—that is, those that lay in the Plane of Shadow itself—were built from shadowstuff in an ordinary post-and-lintel design. Despite appearing indistinct and even insubstantial, they were sufficiently sturdy, at least on the Shadow Plane.

The god Mask, Lord of Shadows, dwelt in a small castle built entirely of raw shadowstuff on the Plane of Shadow. Known as the Shadow Keep, it was shrouded in shadows and nigh impossible to even get a glimpse of against the background darkness of the plane, even up close and in magical daylight.

In the Black Rift in the Shadow Swamp, Despayr and the cultists of Shar who served him employed shadow bellows to collect shadowstuff. These magic pumps drew the substance from the fabric of the plane, then channeled it to his ritual chamber to power his efforts to tear a hole in the Weave.

Tapestries of woven shadowstuff were even used as decoration in the House of Hidden Masters in the city of Chaulssin.

Powers
An item made of shadowstuff was usually an impermanent creation, usually dissipating in a few years or even a matter of minutes, typically comparable to the product of a major creation spell. Naturally, this limited their appeal and application. Only cloakers knew the secret of crafting permanent shadowstuff objects, or rather, of maintaining their existence. According to the sage Saibh yi Saelmur, cloakers could create longer-lasting shadowstuff items if they spent more time on the work.

An object made of shadowstuff weighed nothing.

A shadowstuff weapon from Rringlor Noroth had the ghost touch and brilliant energy powers, except that it shed darkness rather than light for 20 feet (6.1 meters) around.

Magic
A number of illusion spells, namely those of the shadow subschool, extracted a small portion of shadowstuff from the Plane of Shadow to add substance to their illusory effects, so they could do real damage and bear weight. Such spells included shadow conjuration and shadow evocation. In particular, the shadow walk spell allowed swift travel over a coiling path of shadowstuff along the border between the Prime Material Plane and the Shadow Plane.The spell shadow dragon could temporarily transform a dragon into pure shadowstuff. Some sages of draconic lore suspected that the deep dragon Dheubpurcwenpyl, who dwelled in the Rift of Dhalnadar and was often mistaken for a shadow dragon, actually made use of this spell.

A number of powers of shadow magic summoned and shaped shadowstuff itself to create solid objects and effects. For example, the carpet of shadow mystery transformed a section of terrain into shadowstuff, having superimposed it with the Plane of Shadow; while the feign life mystery infused objects with shadowstuff toanimate them. Greater flesh fails infused a creature’s body with shadowstuff to weaken it, while languor poured shadowstuff into their shadow to weigh them down or pull them back. A shadowsmith specialized in drawing shadowstuff from the night to craft tools and weaponry.

A high-level shadow adept, a practitioner of Shadow Weave magic, could create a “shadow double”, a detailed and animate duplicate or his or herself woven of shadowstuff.