The Multiverse is everything that we currently know to exist beyond our own Universe. Unlike the Omniverse, which is a speculation that even the brightest of minds find hard to grasp, the Multiverse has been confirmed by billions of species to be a fact. Its structure, however, is highly debated; mainly due to how contact between many different Universes were facilitated by devastating cosmic events, rather than intelligent manipulation.
The Multiverse is expressed as a function of existence that is composed of ten dimensions, as in accordance with String Theory. Many universes suspended in the "Multiversal Sea" are third dimensional, with fourth dimensional universes only existing as regions of time in the Multiverse itself. In the Omniversal Theory, the Multiverse is assumed to be a "wave" upon the surface of a greater Omniversal Ocean that possesses an infinite variety of dimensions and planes of existence.