The Mainstream Universe is the shared fictional universe where most comic book titles published by Mainstream Comics take place, including those featuring Mainstream's most popular titles, such as Cyberknight, Renegades, Flare, Nightveil and WestGuard.
The Mainstream Universe is further depicted as existing within a "multiverse" consisting of a number of separate universes (sometimes referred to as "realms", or "planes"), all of which are the creations of Mainstream Comics and all of which are, in a sense, "Mainstream universes". In this context, "Mainstream Universe" is taken to refer to the Mainstream continuity in which Earth exists (also called the "Earth realm").
(The Kalos Universe does not exist within this framework. The spaciotemporal relationship between the Mainstream Universe and the Kalos Universe is not yet understood.)