Labyrinth is a zone in Sonic Heroes 2. It is a large maze that serves two purposes; a massive maze where Team Covert live, and on its outskirts, a place of practice for Team Babylon. Neither team know about each other - AWN of Team Covert are aware of an occasional caterwaul during the day, but not of its cause.
Labyrinth did not originate from fanon, and more information can be found on their respective wiki(s). You may read more about it on the following wiki(s):