The Multiverse—a boundless expanse of worlds, each different from the last. These worlds, called planes, differ as widely as the imagination. One plane might be covered entirely in dense jungle, for example. On another, city has replaced nature entirely. Still others are volcanic, icy, barren, or more like our own world, with many varied elements.
Most planes are spheres with an atmosphere and one or more suns and moons; they resemble planets. But there is no law of physics common to all planes of the Multiverse. Planes can be infinite expanses of matter, tiny specks of empty space, or logic-defying inversions of normal reality. A plane can contain an entire, sprawling universe or nothing at all.
Only one thing unites all the planes of the Multiverse: mana, the energy that fuels magic. Mana infuses the land, and only those with a connection to the land can call upon its mana. Some planes are far richer in mana than others. On those planes, magic is powerful and commonplace. Elsewhere, where mana is scarce, magic is rare.
Average beings have no idea that planes exist beyond their own. They live their lives believing their world is the only world. Their perception is limited by the scope of their experience, cut off from the rest of the Multiverse. Only planeswalkers know the greater truth: that each plane is but one of many, and that only they can travel to planes beyond their own.
All planes are connected by the substance of the Multiverse itself: the Æther, called the Blind Eternities by planeswalkers—the only beings who ever see it. In this chaotic, surreal expanse of uncontained energy and matter, time, distance, and the senses have little meaning.
Their ability to cross the Blind Eternities is not the only thing that makes planeswalkers different from every other being in the Multiverse. That ability leads them to form connections with many different lands, to encounter hundreds or even thousands of different races and creatures, and to learn a vast array of spells—more than most archmages bound to a plane could ever hope to master.
The vastness of the Multiverse and the wonders it holds...that is what unites all planeswalkers, what drives them forth, through the Blind Eternities and into planes beyond their own.