The mo'arg are powerful and highly intelligent demon members of the Burning Legion. They are extremely diverse, with subspecies ranging from stunted gan'arg and imposing felguards to colossal brutes and fel lords. A demonic species hailing from the Twisting Nether, the mo'arg were some of Sargeras' opponents when he was still the defender of the Pantheon. After Sargeras betrayed the Pantheon, the highly resourceful and industrious mo'arg were recruited into the Legion to serve as armorers, forging fel-infused weaponry and constructs to besiege the worlds of the cosmos.
Brutish though they may seem, these iron-stitched horrors are exceedingly brilliant engineers and forge-smiths. Their black iron constructs have sown death across a thousand worlds. Many mo'arg are tinkerers, scientists, blacksmiths, and engineers that have "improved" their own bodies with bionic parts. Others instead serve the Legion armies as felguards. Fel lords are speculated by some scholars of the Legion to be an evolved version of the felguard.
Even with muscular, tall and broad build, many mo'arg have improved their own bodies with bionic parts. A sickly green substance runs trough their veins, bleeding from their sharp-toothed mouths and from incisions in the torso and around neck; metal stitches barely maintain their patchwork skin. They are hairless and their feet display two front claws and a rear single claw. When not replaced with a bionic part, mo'arg eyes are white and seemingly without pupil.
So-called "mo'arg brutes", such as Smashspite the Hateful, forego the engineering that their race is known for in favor of wielding massive weapons and fighting on the front lines. They are much more imposing and powerful than other mo'arg.
The gan'arg sub-race bears little resemblance to the mo'arg mother race, being stunted and weak to the point that they seem far more similar to kobolds than they do the gargantuan demons of the Burning Legion. However, they are often just as intelligent and cunning as their mo'arg masters and should not be underestimated.
Not all mo'arg are loyal to the Burning Legion. The Maker serves the Fel Horde, members of the Illidari loyal to Illidan Stormrage, and at least one independent mo'arg has even been allowed inside the walls of Shattrath City.
- Main articles: Felguard#Notable, Mo'arg brute#Known, Fel lord#Known
- Under the guidance of uncooperative mo'arg engineers, demon hunters were able to create several portals to Mardum.
- Some mo'arg have gone so far with their enhancements that they resemble the abominations of the Scourge, with the only difference with their undead counterparts being that they are actually very clever (as well as very alive).
- In Legion, the mo'arg's role as engineers seems to have been dispersed throughout other demons, with the antaen Kin'garoth taking the position of chief engineer for the Legion. Meanwhile the gan'arg's role was mostly given to wyrmtongues, with non-felguard mo'arg presence being only maintained by brute frontline soldiers, though some gan'arg can be seen on the Broken Shore.
- Fan art