Tainted orc

Tainted orcs are orcs corrupted by demonic energies.

Introduction
Orcs once cultivated a shamanistic society upon the dying world of Draenor. Then the dark magics of the Burning Legion corrupted them. Lured to the world of Azeroth through a dimensional gateway, they were manipulated into waging war against human nations. Recently, most orcs threw off the shackles of demonic influence and now strive to recover their lost heritage. Some orcs remain under the thrall of the Burning Legion, however, to the point where they are twisted into mockeries of their former selves.

History
After their defeat in the Second War, most orcs suffered from a lethargy produced from the withdrawal of the demonic forces. Thrall, an uncorrupted orc, was able to rekindle their original shamanistic ways, and many of them threw off the shackles of demonic influence and now strive to recover their lost heritage. During the Third War, Grom Hellscream killed Mannoroth, thus breaking the bond that kept the tainted orcs corrupted. From then on, tainted orcs were able to return to their original ways. However, some orcs remain under the thrall of the Burning Legion by their own decision, to the point where they are twisted into mockeries of their former selves. Fel orcs are the ultimate step in being corrupted by demonic energies.

Green orcs
Even though some orcs did not consume the blood of Mannoroth, the demonic energies coursing through Draenor were so strong, that they were too partially turned into tainted orcs, at least in their skin color, which turned from brown into green. Those that did consume the blood turned into a brighter shade of green, and suffered from more transformations, as mentioned above.

Reversion
It is not known if tainted orcs can become uncorrupted orcs again, although Thrall and his new Horde are trying to recover their lost customs. In Warcraft III, it was seen that fel orcs have a chance to go back into tainted orcs, as shown when Grom Hellscream, who was a fel orc for a short time, was able to become his former self with Thrall's help and the combination of orc shamanism and elven magic.

Appearance
This creature looks much like an orc but of massive size, standing perhaps 8 feet tall. Its green skin is mottled with gray and its dark hair hangs in thick tangles. Its eyes shine with a crazed, savage light.

Culture
Orcs appear to other races as a barbaric and brutal people, but they are proud and noble in their way. Those subject to demonic taint give vent to their brutish ways, however. A tainted orc can channel his warrior fury to become truly fearsome in combat.

Trivia

 * Tainted orcs seem to be a stage between green orc and chaos orc, like Grom Hellscream iconically was before his death.