The Multiverse is the near-infinite number of different planes. Nobody really knows how many planes there truly are.
A plane is a self-contained world or universe of any size found within the multiverse. While planes can be governed by any conceivable set of rules and natural laws, or even indeed inconceivable ones, most planes visited in the storyline are comfortably similar to Earth.
Blind Eternities Edit
Blind Eternities is a term commonly used by planeswalkers to refer to the space between planes in the Multiverse which is filled with chaotic energies, mainly theÆther but also mana and temporal energy. Only planeswalkers, and the most powerful, godlike beings can enter it and survive its rough environment. The Æther takes part in summoning creatures, from which that creature materializes, or is pulled from.
The Eldrazi are creatures native to the Blind Eternities. It is not known if they were born there, or later adapted to survive its rough energies.