|This article contains canon information corresponding to the Tales of Arcadia franchise. That means all information in this article is true and has appeared/been validated officialy on-screen.|
Gumm-Gumms were a group of evil Trolls lead by their king Gunmar. They were sealed away into the Darklands by Deya the Deliverer and yearn to wage war with Earth and conquer it. In Trollspeak, their name means "bringer of horrible, slow, painful and thoroughly-calculated death". The only Gumm-Gumm Troll that avoided imprisonment the Darklands is Bular, son of Gunmar, who then laid a scheme to free his father and his armies.
The Gumm-Gumms are distinguished by their black-colored skin, their large size and their glowing eyes. The Gumm-Gumms live only to fight and murder and are the enemies most feared by the other Trolls.
The Gumm-Gumms were originally just unorganized tribes of barbaric Trolls until Gunmar killed their original king, Orlagk, and took control, while banding them together into a fearsome army. Their main goal is to take control of the surface and devour all humans.
It seems that a troll can actually change into a Gumm-Gumm as seen when a Krubera trolls can become a Gumm-Gumm, like AAARRRGGHH!!!, and Dictatious. Physical changes can be seen when AAARRRGGHH!!! becomes violent and looks more similar to Gumm-Gumm trolls.