|This location exists primarily or exclusively within the Pre-Super Genesis Wave continuity.|
Information in this article may not be canonical to the storyline of the games or any other Sonic continuity.
Demon Island, formerly known as the Sunken Island is Anti-Mobius's version of Mobius Prime's Angel Island. As its name suggests, it is an island sunken under the sea with an air bubble to provide its occupants with air. The Demon Island's history is never explained. Like its Mobius Prime counterpart, it is also home to the Echidna people, with O'Nux serving as the guardian of six Anarchy Beryl.