Fel orc

The fel orcs possibly chaos orcs are the ultimate culmination of the Burning Legion's control over the orcs.

An orc becomes a fel orc after consuming the blood of a pit lord. Then, a heavy blood haze falls over the orc, forcing him into a crazed bloodlust. The most prominent side effect of this blood haze is a deep red discoloration of the flesh and insane desire for battle and violence. Fel orcs are also more powerful than regular orcs, having chaos damage on all their attacks.

History
The only instance in which fel orcs were active on Azeroth was during the Third War. Mannoroth tricked Grom Hellscream and his Warsong warriors into drinking his blood from a tainted fountain of health. Grom later overcame the blood haze with the help of Thrall and Jaina Proudmoore and slew Mannoroth, thus freeing both the fel orcs and the orcs that had been corrupted by Manoroth on Draenor.

When the pit lord Magtheridon took control of Outland, he created fel orcs by corrupting them with his blood. Fel orcs made up the backbone of Magtheridon's armies. After Magtheridon was defeated by Illidan and imprisoned, the fel orcs stayed in Hellfire Citadel, keeping guard over the captured pit lord. This is the first known appearance of the fel orcs in World of Warcraft. They no longer serve the Burning Legion but follow Illidan instead. Illidan has continued using the blood of Magtheridon to create more fel orcs to follow him. A letter recovered from one of the orcs has revealed that Illidan is not pleased with the orcs' progress with the defense of the Blood Furnace. It also seems they are experimenting on captured Mag'har to create fel orcs.

Cataclysm
In World of Warcraft: Cataclysm fel orcs from the Dragonmaw clan came from Outland to and enslave the rest of the Dragonmaw on Azeroth. They are later defeated by the Horde to help free the rest of the clan.

Physiology
The standard fel orc has red skin, and a ridge of long sharp spines coming out of its back. Bony horns grow from its arms and hands. Its eyes are bloodshot and glow red, and six long and thin fangs grow out of its mouth. Its ears are stubbier than orc ears, coming to a blunt point. Most fel orcs have lived for years in Outland with the corruption, and this has led to the greater mutations.

Relation to tainted orcs
Tainted orcs is the RPG's term for green orcs, that is, the orcs that were corrupted by the Burning Legion's influence on Draenor. These orcs appear to be different from fel orcs, as they don't posses the physical attributes of a fel orc. The exact relation between tainted orcs and fel orcs has not been stated. It can be noted, though, that the transformations suffered by tainted orcs are less severe than those suffered by fel orcs.

Tainted orcs may be something of a "first step" towards a fel orc. The turning into tainted or fel orc may be related to the amount of pit lord's blood consumed. Grom Hellscream was a tainted orc when he consumed for the second time the blood of Mannoroth, so maybe either becoming a tainted orc and then consuming more, or simply consuming a large amount of blood, is the trigger to become a fel orc. Consuming less blood could result in just a tainted orc.

Official site info


From The Burning Crusade Bestiary:


 * Mystery and speculation surround the corrupted fel orcs who recently appeared in Outland. Though little is known about these savage warriors, the most disturbing revelation to come to light is that their numbers appear to be steadily increasing. Even more perplexing is the fact that the orcs have discovered some alternate source of fel energies to feed upon, despite the slaying of Mannoroth and the Horde's subsequent release from demonic corruption. Regardless of their connection to fel energies, however, it is believed that this new breed is not working with the Burning Legion. What authority they do answer to remains a mystery.

In The Burning Crusade, it is revealed that the reason that the fel orc numbers are steadily increasing is because they're simply manufacturing more of them. Inside the Blood Furnace, an instance within Hellfire Citadel, adventurers come to find the process by which they're using Magtheridon's blood to create more fel orcs. They also face a boss named The Maker, who is likely overseeing much of the process, under orders from Illidan.

Known corrupted clans


Several corrupted clans (or long-lost elements of clans in Azeroth) have been discovered in the general vicinity of Hellfire Citadel:


 * Bleeding Hollow clan - What remains of the clan that brought forth Kilrogg Deadeye has succumbed to corruption. Those that remain uncorrupted seek refuge in Garadar in Nagrand. They serve as archers, warriors, and casters.
 * Bonechewer clan - A clan attacked by the Shadowmoon clan for possession of the Skull of Gul'dan; serving primarily as warriors and casters.
 * Dragonmaw clan - The infamous clan of Zuluhed the Whacked once known for their domination of the Red Dragonflight and Alexstrasza; now continuing their dragon riding trade with the nether drakes through the subjugation of Karynaku.
 * Laughing Skull clan - Attacked by the Shadowmoon clan to regain the knowledge necessary to reopen the Dark Portal; serving primarily as rogues and enforcers.
 * Shattered Hand clan - Clan of Kargath Bladefist, currently serves as the Guild of Rogues in Orgrimmar; they serve as warriors and enforcers, though a small number of casters have been seen around the Citadel.
 * Shadowmoon clan - The former clan of Ner'zhul; primarily warlocks and channelers of the blood of the captured pit lord Magtheridon.

Famous fel orcs

 * Bloodgrin
 * Bonethirst
 * Blackrock Slave Master
 * Gorgosh
 * Grom Hellscream (Chaos orc) (drank the Blood of Mannoroth from the Chaos Well)
 * Keli'dan the Breaker
 * Maim
 * Mizgill
 * Nera'thor
 * Rend
 * Sagra'nel
 * Jubei'Thos
 * Kargath Bladefist
 * Gurtogg Bloodboil