- "Looking up slightly at the massive root structure above, Scotti saw something wriggle past. An eight-foot-long, armless, legless, colorless, boneless, eyeless, nearly shapeless creature, riding the roots."
- ―Waughin Jarth[src]
Rootworms were creatures that were native to the swamps of Black Marsh,[1] the homeland of the Argonians.[2] They were massive worms that rode along the roots of the trees under the swampy water of Black Marsh.[1] They had thin skin as well as breathing holes that travelers could make use of to enter rootworms' stomachs and ride inside them.[1] This method of travel was referred to as the Underground Express.[1] They were approximately eight feet long and were colorless. They also did not possess eyes or bones.[1]
During the winter in Black Marsh, the rootworms migrated from northern regions and towns such as Hixinoag to southern regions and cities such as Gideon.[1] They were also extremely fast and could cover the distance between Hixinoag and Gideon in several hours.[1]