A Shadow Dragon is a rare species of planar dragon from Dungeons & Dragons that has a connection with the Plane of Shadow, either being a native to the plane or a dragon that has been corrupted by the plane’s dark magic. Dragons that fall in the latter category usually become corrupted after entering a portal that leads to the The Plane of Shadow where they are stranded, these portals being known to spawn in places a dragon might make its lair. Once they are corrupted, they cannot revert back even if they return to the Material Plane.
Shadow Dragons are distinct for their dark lavender scales and translucent wings, the darkness of their bodies making them appear like a "foreboding mass of shadows". They have two head fins that run down their serpentine neck as well as a blue tail fin with black spines that serves as a swimming fin. Corrupted dragons look similar but retain their basic structure, a Shadow Red Dragon for example would still have its swept back horns, frill, and singular upper fin.
Shadow Dragons have purple eyes and have an average length of 20-30ft.
Corrupted dragons retain their personalities, although the longer they stay in the Plane of Shadow, the more they will be influenced by the evil nature of the plane. The Dragons may or may not want to reside in the Plane of Shadow, either embracing its dark clutches or wanting to return to their home plane. Those that do want to return to their home plane may want to return in order to spread the evil of the Plane of Shadow, or may just want to return since it is easier to obtain power and treasure back from where they came from.
Shadow Dragons will eat anything, although favor carrion. They will often let their slain prey rot out in the open until it is properly fouled. 
Shadow Dragons prefer to attack their foes from hiding, being able to magically blend in with any dark environment as well as teleport in between shadows, all on top of already being naturally stealthy creatures. They also utilize illusion powers to confuse their foes.
Shadow Dragons are by and large solitary creatures, the chance of seeing two Shadow Dragons mating being an extremely rare occurrence, although some Shadow Dragons may live in clutches of 2-5. Adult and older Shadow Dragons may have families of up to 5 children.
Shadow Dragons tend to enslave lesser races, particularly the Shadar-Kai, who then serve as the dragon’s servants and soldiers. Shadow Dragon will also lurk near communities of other races "that can alert them to potential foes or victims."
Lairs and Terrains
Shadow Dragons hate being in the light, but hate being in complete darkness as well, thus Shadow Dragons make their lairs where shadowy light is present for most of the day on the Material Plane, preferring ancient ruins. In the Plane of Shadow, they live in dense forests, castles, and labyrinth caves.
Powers and Abilities
Shadow Dragons can breath a torrent of shadows that drain the energy out of their targets. They can also manipulate the shadows around them to blend in with it or summon individual shadows that can attack their foes. The dragons have several spell-like abilities that enable them to conjure illusory duplicates of themselves, become undetectable by divination magic, and teleport vast distances. They are resistant to magic, and hold immunity to energy draining effects.
Corrupted Dragons possess a shadow breath as well, which has the additional effect of animating the shadows of the foes that die from the attack which become its servants.
- Mike Mearls, Jeremy Crawford, Christopher Perkins (2014) Monster Manual 5th Edition pg.84-85 Wizards of the Coast
- Andy Collins, Skip Williams, James Wyatt (2003) Draconomicon: Book of Dragons pg.191-192 Wizards of the Coast
- Bruce R. Cordell, Ari Marmell, Robert J. Schwalb (2008) Draconomicon: Chromatic Dragons pg.199 Wizards of the Coast
- Gary Gygax (1983) Monster Manual II pg.58-59 TSR Inc.
- Grant Boucher, William W. Conners, Steve Gilbert, Bruce Nesmith, Chris Mortika, Skip Williams (1990) Monstrous Compendium: Greyhawk Appendix TSR Inc.