"Brutish though they seem, these iron-stitched horrors are exceedingly brilliant engineers and forge-smiths. Their black iron constructs have sown death across a thousand worlds." - Exodar Holographic Emitter in the Vault of Lights.
Many mo'arg are tinkerers, scientists, blacksmiths, and engineers that have "improved" their own bodies with bionic parts.
The mo'arg are a demonic species resembling the undead Flesh giant and Flesh Titan. Mo'arg serve within the ranks of the Burning Legion. Tall and broad in stature, they are particularly proficient in hand-to-hand combat. Many mo'arg are tinkerers, scientists, blacksmiths, and engineers among the ranks of the Legion and have "improved" their own bodies with bionic parts. Some have gone so far with their enhancements that they resemble the abominations of the Scourge, though unlike their undead counterparts they are actually very clever (as well as very alive).
The gan'arg subrace bears little resemblance to the mo'arg mother race, being stunted and weak to the point that they seem similar to kobolds rather than the typical gargantuan demons of the Burning Legion. However, gan'arg are often just as intelligent and cunning as their mo'arg masters and should not be underestimated.
Some mo'arg seem to serve their own agenda, and are not hostile to players.