At the apex is the Positive Energy Plane, the headwaters of the multiverse. Legend holds that the plane was briefly extinguished during the War of Ascension, but the new gods soon reestablished it, though no one knows how. Did they just will it back into existence? Or is the furnace of creation fueled by something more sinister?
Regardless, the Seven Heavens lie directly below, basking in the eternal light of the Positive. But the Heavens aren’t perfect—the energy of creation is still unstable at this point, and straying too far from the great mountain at the center is almost certainly a one-way trip to the edge of the Far Realms where matter, energy and spirit lose their coherence and start to mix.
From there, the river of energy pouring out from the Positive begins to develop into the elements that compose the rest of the multiverse. A raging Limbo of fire, earth, air and chaos soon forms. Limbo is a terrifying place, where the sky is made from half-formed thoughts and the ground is just as often fire or water as earth. It is also a place where even mortals can be gods, and a strong enough mind can force the elements around them to form anything they can conceive and will into being. Some say that Limbo is really all there is, and any other plane is just a pocket of Limbo willed into a certain form by the beliefs of those within.
Somehow, the Material Plane exists as a bubble of sanity in Limbo. It’s here that mortals are born, live, and die. Few learn much about the other planes, and even fewer ever reach them. But the reverse is far from true—as fiends, angels and other outsiders form from the souls of the deceased, and only mortals can make more mortals, the Outer Planes have a vested interest in what goes on here. But these souls don’t always go right to their final reward or punishment.
Also adrift in Limbo is the caged city, Sigil, the crossroads of the multiverse. Sigil’s reputation as the “City of Doors” is well earned. A canny traveler can find a gate to most anywhere with enough looking. But every door has a key, whether it’s a literal key, an innocuous object, or a state of mind. Without their particular key, a portal is nothing more than a mundane doorway or a lifeless arch. An unlucky “resident” can spend a lifetime hunting for the key to get out via a portal that turned out to be one way.
The Far Realms ring the edges of Limbo, at the base of the Astral Sea. They used to be a myriad of planes, from the blessed fields of Elysium to the rugged mountains of Aborea and the hopeless expanse of the Gray Wastes. Now, the separate planes are slowly dying, without the old gods to sustain them. The festhalls on Ysgard have turned to ruins, and the villages of Arcadia to ghost towns. Occasionally, some of the Blood War between demons and devils spills out onto the old planes. For the most part, though, there’s no one here to watch as a universe crumbles.
Beneath the Far Realms, sanity is no longer required. Baator, the Nine Hells, lie at one end. Opposite the Nine is the Abyss, a crack in the multiverse through which demons spawn from parts unknown. Between the two is Pandemonium, narrow caves through which the last gasps of energy from the Positive Energy Plane flow. At the end of it all, beneath even Vecna’s Last Fortress, is the Negative Energy Plane, the all-consuming terror beneath creation.