The Broken Ring

The Ring of the Heavens

After their victory over the primordials in ancient times, the gods decided to end the threat for good. In concert, they forged a great ring, a containment for the remaining and free-willed primordials, a containment for the Elemental Chaos.

On this ring, 16 "outer" planes were arranged  in perfect symmetry, corresponding to the alignment of its inhabitants (lawful, chaotic, good, evil, and differentiations between). The Outands, a 17th, neutral plane capped the trapped Elemental Chaos and hid it from the sight of the gods.

Those primordials that were too powerful had to be contained on the planes, in the reach of the Gods. Many primordials were imprisoned on Carceri, the prison plane, others in remote layers of the planes of good deities, some were hidden in maelstroms of Limbo, a mocking imitation of the Elemental Chaos.

Some whole fractions of the elemental chaos, though, were too difficult to control, so whole outer planes had to give room for the Abyss or the domains of the Slaad.

Under the influence of the symmetry of the ring, the Elemental Chaos was slowly divided and formed into the "inner" planes: 4 elemental, 4 paraelemental, 2 energy, and 8 quasielemental parts, diminishing the raw entropic powers of the primordials that remained free in the multiverse.

The Gods could then tap the power of the Inner Planes to build magnificent realms on the Geat Ring, and the various pantheons of gods worshipped on similar worlds even shaped additional connections and crossroads between their realms, calling them The Great Wheel, The Great Road, Tree of Worlds, the World Ash, Styx, The River Ma'at, or The Twelve Hours of Night, linking to several dominions and allies of the Gods.

For eons, the planes remained in this order as it was imposed by the gods. But then a series of events turned the tides in favor of the primordials, who stirred in their seemingly eternal prisons.

The Shattering

The machinations and powers of primordials like the Greek Titans and demon lords, plus the interference of aspiring Asmodeus, rogue gods, and some meddling mortals, changed the balance of power lately in favor of the primordials.

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The Spellplague

For example, a world called Abeir-Toril was rocked by a cataclysm referred to as the 'Spellplague'. The world's deity of magic, Mystra, who spanned the world with a field of magic called the Weave, was slain. The Weave was created to limit this world's magic, so that mortals and immortals alike could not access the power of raw magic, with some exceptions.

Abeir-Toril had been known as a main battleground between gods and primordials in ancient times, and many primordial corpses and prisons were contained on this world. Mystra's Weave also hid the primordial prisons and barred their raw, elemental influence from the world.

Mystra had been slain several times in Abeir-Toril's history, but this time, her essence was so utterly destoyed, that the Weave ceased to exist. Raw chaos and magic raged across the lands, slaying wizards or driving them mad, the ground was raised, lowered, or thrust into the air, and, unknown to many, the primordial prisons were uncovered, their influence slowly starting to taint the surrounding lands.

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As a result of this rise in power, the inner planes suddenly started to flow into each other again, unlocking their entropic potential, and expanded. The ring of the outer planes unhinged, and the great ring fell apart. The planes were rocked by chaos and destruction, but the deities and other denizens of the planes were able to keep much of their realms and dominions safe.

When the chaos cleared and the mists lifted, the gods had transferred their homes to the Astral plane,  floating like islands in a vast sea, while the primordials and demons once again consolidated their power in the reborn Elemental Chaos.

The Ethereal plane was dissoluted and enveloped by the Elemental Chaos, while the planes of Shadow and Faerie assumed new positions in the new order of the cosmology.

Sigil in its function and features was unaffected, but many portals became broken or switched destination, especially those targeting the Elemental Chaos. The central parts of the neutral Outlands and its spire still float somewhere in the endlessness of the astral sea, and on the chunks of matter orbiting around it, new towns and life springs up around portals leading to the scattered divine dominions, similar to the 'Gatetowns' of the former outer planes.

While some worlds, especially those with many portals, suffered greatly, most worlds were protected from the planar tumults by divine intervention or other powers like the primal spirits of the world.

Still, the primordials power is not great enough to challenge the gods, as many are asleep, imprisoned or wait to be raised from death, but they are back on their feet, and the cosmic game, with the prime worlds as its prize, is starting anew...