Fel orc

The fel 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 a second time. 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. This even affects the unwilling as revealed in the Blood Furnace. 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 Mannoroth 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. 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.

Caza'rez of the Horde is working on a cure for the Fel Orcs converted by the Illidari.

The 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.

Warlords of Draenor
After the Iron Horde has suffered many serious losses, Kilrogg accepts Gul'dan's renewed offer of demon blood. What he subsequently transforms into has also been described as a fel orc, though of a seemingly different variety as he is grey in color, instead of red, and possesses massive deformities.

Appearance
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.

Trivia
(TBA)