"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 in servitude to the Burning Legion. Though the resemble the undead Flesh giant and Flesh Titan, they are a race of truly proficient scientists, engineers, tinkerers and blacksmiths. To enhance their service to the Legion ans their own efficiency, many members of this patchwork race have "improved" their own bodies with bionic parts. Some have gone so far with their enhancements that they resemble the abominations of the Scourge.
The gan'arg, a subrace of the mo'arg, bear little resemblance to the mo'arg mother race, being stunted and weak to the point that they seem similar to kobolds. 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.