The multiverse (or meta-universe) is the set of multiple possible universes (including the historical universe we consistently experience) that together comprise everything that exists and can exist: the entirety of space, time, matter, and energy as well as the physical laws and constants that describe them. The term was coined in 1895 by the American philosopher and psychologist William James The various universes within the multiverse are sometimes called parallel universes.
Known types of parallel universes include alternative universes, quantum universes, interpenetrating dimensions, parallel dimensions, alternative realities, alternative timelines, and dimensional planes, among others.
There are several known subgoups of universes including, but not limited to, the following:
- The Amber Expanse An ongoing war for domination over parallel realities being fought between the kingdoms at the extreme ends of Shadow—Amber, the one true world of Order, and the Courts of Chaos. Amberites of royal blood—those descended from Oberon (and ultimately his parents: Dworkin, formerly of the Courts of Chaos, and the Unicorn of Order herself) —are able to “walk in Shadow”, mentally willing changes to occur around them. These changes are, in effect, representative of the Shadow-walker passing through different realities. There are apparently infinite realities, and the characters in the novels are not sure if these different universes are created as one walks through Shadow, or if they already exist and a Shadow-walker is able to slip from one to another. In the Merlin cycle there are references to the Wheeler-Everret interpretation of quantum-mechanics and the Ghostwheel created by Merlin is said to “shuffle” through Shadows, suggesting that the multiverse exists independently, although this is never explicitly stated.
- The Blood of Krypton The structure of the Multiverse is described as a web of 196,833 universes arranged in a pattern resembling a snowflake, each universe separated from its neighbors by a medium called the Bleed. In the Batman-Planetary crossover, it is said that a “partial multiversal collapse” occurred in 1985, an oblique reference to Crisis on Infinite Earths. The fact that it is only a “partial collapse” indicates that there were definitely still other realities, and that the Multiverse was not as “gone” as was originally believed. At about the time of Infinite Crisis, the Bleed was shown to lie between the 52 dimensions
- Worlds of Marvels Starting with issues of Captain Britain, the main continuity in which most Marvel storylines take place was designated Earth-616, and the multiverse was established as being protected by Merlyn. Each universe has a Captain Britain designated to protect its version of the British Isles. These protectors are collectively known as the Captain Britain Corps. This numerical notation was continued in the seriesExcalibur and other titles. Each universe of the Multiverse in Marvel also appears to be defended by a Sorcerer Supreme at nearly all times, appointed by the mystic trinity of Vishanti to defend the world against threats primarily magical in nature from within and beyond and bearing the Eye of Agamotto.
- The Champion’s Spheres Common to these universes is the concept of an Eternal Champion who has potentially multiple identities across multiple dimensions. The Multiverse contains a legion of different versions of Earth in various times, histories, and occasionally, sizes. One example is the world in which his Elric Saga takes place. The multiplicity of places in this collection of universes include Melniboné, Tanelorn, the Young Kingdoms, and the Realm of Dreams.