Demons are beings of evil, varying a lot in looks, living on many planets across the universe. Avatarian demons lives in Hell. Demons can curse non-demonic creatures with a demon-virus, by sending fel energy into their bodies, which will make them half-demons. Demons have their own unique language, but it is rarely used.

Only two known Avatarian demons have appeared in the Avataria-series; Kakuslor and Clarox.