Shadow Fiend

From Dungeons & Dragons Monster Manual (2014):

When a demon’s body is destroyed but the fiend is prevented from reforming in the Abyss, its essence sometimes takes on a vague physical form. These shadow demons exist outside the normal abyssal hierarchy, since their creation results most often from mortal magic, not from transformation or promotion.

Shadow demons all but disappear in the darkness, and they can creep about without making a sound. A shadow demon uses its insubstantial claws to feast on its victim’s fears, to taste its memories, and drink in its doubts. Bright light harries this fiend and shows its distinct shape, resolving it from a blur of darkness to a winged humanoid creature whose lower body trails off into nothing, and whose claws rend a victim’s mind.

Shadowy Nature. A shadow demon doesn’t require air, food, drink, or sleep.

From Planescape: Monstrous Compendium Appendix II (1995):

Shadow fiends have no known language, although it is said that they can communicate with other creatures from the Lower Planes. No mortal has ever confirmed this. however.

Shadow fiends live in small villages throughout the Lower Planes. They have a high sense of the aesthetic. and their villages are noted for the sculptures of pure darkness. (Shadow fiends cannot use the ability to sculpt darkness outside of the Lower Planes, and the time and concentration required to do so prevents its use in combat.) 

Many villages are built around a gate to some other plane. These gates are tiny (only a few feet tall) and well hidden. if trapped on a foreign plane, shadow fiends seek and dwell with ancient black dragons. Some speculate that the shadow fiends have some biological tie, or perhaps even social ties, with these evil dragons. Certain researchers of magic would find confirmation of this rumor valuable

Shadow fiends are a race of traders in the Lower Planes. They deal in minds that they have captured in dark gems. An imprisoned intellect of great power and lore, such as a wizard with a high reputation, can interest many buyers and provoke intense bidding wars. The shadow fiends trade the captured intellects for raw evil magic, which they shape by unknown processes into more shadow fiends. 

Shadow fiends seek powerful minds to imprison and sell, but sometimes they inadvertently steal the intellects of braggarts and know-alls. These little minds, prone to brag of their status, thereby attract a shadow fiend’s notice. Soon the victims find themselves on a trading block in the Lower Planes.

Some say the powers of the Lower Planes have close ties to the shadow fiends, and that the powers can command the fiends to do their bidding Some say the powers of the at any time.

Combat: Like shadows, which many believe (wrongly) are related creatures, shadow fiends are 90% undetectable in 5 dim light or shadows. When they attack those who have not spotted them, they always gain surprise. Each round the monster can strike with two claws (ld6 damage Whenever the shadow fiend gains surprise, it springs onto its victim. Because of the small wings on its back, it can leap up to 30’ and strike with four claws (each doing ld6 damage). When it leaps, it cannot use its bite attack. In combat, the power of the creature depends on the lighting in the area. bright lighting In brightly lit areas (open sunlight or a continual light spell), the shadow fiend is greatly weakened; its Armor Class is 9 and all attacks that strike it inflict double damage. Because of this, shadow fiends flee from each) and bite (ld8 damage.) 

Whenever the shadow fiend gains surprise, it springs onto its victim. Because of the small wings on its back, it can leap up to 30’ and strike with four claws (each doing ld6 damage). When it leaps, it cannot use its bite attack. In combat, the power of the creature depends on the lighting in the area.

Bright lighting: In brightly lit areas (open sunlight or a continual light spell), the shadow fiend is greatly weakened; its Armor Class is 9 and all attacks that strike it inflict double damage. Because of this, shadow fiends flee from opponents in bright light.

Dimmer lighting (torch, lantern, or a light spell): The shadow fiend is somewhere better off. Here, it has Armor Class 5 takes normal damage from attacks, and gains +1 on its attack rolls.

Darkness (anything up to candlelight or moonlight): The creature is at its deadliest. It gains +2 on all attack rolls, it has Armor Class 1, and all damage done to it is halved.

Regardless of lighting, the shadow fiend is immune to damage from fire, cold, and electricity. A light spell cast directly upon the creature inflicts ld6 points per level of the caster, although this dam

Once per day the shadow fiend can cast a darkness, 15’ radius spell or subject all persons within a 30’ area to a fear spell. Once per week, it can cast a magic jar spell at a single target, provided that it has a suitable receptacle for the victim at hand. If the victim of the magic jar attack saves vs. spells, the shadow fiend is stunned and cannot act for ld3 rounds. Shadow fiends can he turned by clerics as “special” creatures on the undead turning chart.