Dark creature

A dark creature was a type of creature that had a strong connection to the Plane of Shadow, possessing a supernatural ability to hide in shadows and other powers.

Description
Dark creatures resembled their counterparts on the Material Plane, though they were strange and distorted reflections. They tended to be much duller in coloration, with skin tones and hair highlights having more gray and black hues, while brighter colors, like yellow or white, almost never appeared upon them. Overall, they seemed more shadowy and eerie. They also weighed somewhat less than an equivalent creature, suggesting a portion of their very substance had been replaced by the "shadowstuff" of the Plane of Shadow.

Abilities
A dark creature possessed a supernatural ability for melding with shadow. Even while being observed and standing in plain sight, a dark creature could hide itself within a nearby shadow, provided there was no daylight or magical light to illuminate them. They were also incredibly stealthy, whether in hiding or creeping about unheard.

Dark creatures also possessed darkvision to a distance of 60 feet (18.28 meters) and superior sight in low-light conditions, being able to see in the dark twice as well as an elf and four times as well as a human. They were resistant to the damaging effects of cold and could move more swiftly.

Ecology
Dark creatures were those that had a certain degree of connection to the Plane of Shadow, whether naturally occurring there or acquiring it with a close connection or exposure to the plane. Not all such creatures could be considered "dark"; some with stronger or weaker connections, even those native to the plane, manifested a shadow nature in a different way, such as in the case of the shadow mastiff.

Natural-born dark creatures were usually found dwelling on the Plane of Shadow, though they sometimes slipped into other planes through weak points in the barriers between dimensions. Any creature could have a dark reflection on the Plane of Shadow; dark lions, dark goblins, and dark umber hulks were all possible.

A dark nature could also be acquired by those who had later in life gained a strong connection to the Plane of Shadow. One means was passing through—and surviving—a failed Shadow Gate. One passage might leave a "seed" of shadow in a being that could be called upon to gain dark powers for some ten minutes a day, while ten or more successful attempts would see a transformation into a full dark creature.

History
In the Year of Lightning Storms, 1374 DR, the priests of Shar at a false Temple of Mystra in Wheloon, Cormyr, tried to create a gate to the Plane of Shadow. Unsuccessful, the result was a failed Shadow Gate. Despite the deaths, they sent many of their number through, as well as their captives, and to be transformed into dark creatures.

Notable dark creatures
Using a failed Shadow Gate, the Sharrans created shadow guards, dark disciples and dark priestesses like Tyrra, and even a dark earth elemental. Halish was one of their victims who could become a dark creature temporarily.