Limbo

Limbo was an Outer plane in the Great Wheel cosmology model that embodied the chaotic neutral alignment. The plane of Warrior's Rest in the World Tree cosmology was similar to Limbo in many ways but not quite as morphic. The batrachi formed a realm in Limbo called the Supreme Throne which became its own plane in the World Tree cosmology model. Limbo was lost during the Spellplague and may have fallen into the Elemental Chaos.

Description
This plane was supreme chaos, a twisting, quicksilver place filled with bits and pieces of rocks, trees, the four elements, entire landscapes, strong winds, and random pockets of liquid, solid, or gas. Sentient beings could dampen down the chaos to livable levels and produce a safe environment as long as they maintained concentration. The size of a safe zone was directly related to the intelligence of the individual controller. Demigods and more powerful beings did not have this burden and indeed could create realms that survived even if they left Limbo. Gravity operated only between solid objects that touched each other and had about the same strength as on most Prime Material Planes. Thrown objects would fly straight until they hit a solid object. Objects with no momentum would hang in space until contacted by something solid.

As described by the Great Wheel cosmology, Limbo had five layers that were nearly indistinguishable from each other. The first four layers were named for the chief race or deity that were most often found there. The fifth layer was referred to as the layer of Lost Gods.

Gith and Slaad
The slaad were likely natives of Limbo and the githzerai were immigrants (or refugees, if you ask the githyanki) and the first layer was named for them. This layer was strategically important because of its connections to Gladsheim, Concordant Opposition, Pandemonium, and the Astral plane.

Susanowo
Named after a deity from the country of Japan on Earth, he ruled a spherical bubble half filled with sea water and aquatic life and churned by storms of his making.

Agni
Named after a deity from the country of India on Earth, he resided in a sphere of pure flame that floated through the layers at his will.

Indra
Also from India, Indra's sphere was half filled with enchanted milk and his palace stood on island-sized tortoise (or possibly a tortoise-shaped island).

Lost Gods
It is unknown if any race or deity favored this layer.

Afterlife
When souls arrived in the plane of Limbo they were not allowed to manifest in some form but rather were absorbed into the matter of the plane. Occasionally a collection of spirits would become powerful enough to form what was called a chaos elemental, not to be confused with a being from the elemental planes.

Realms
The realms of the powers that resided in Limbo floated through the various layers at will and so are listed here in no particular order.
 * The slaad lords Ssendam and Ygorl maintained realms most often found in the first layer but away from areas not under their control. Ssendam's citadel is a golden castle, while Ygorl's realm is a chain of carved spheres that whirl about.
 * The githzerai formed hamlets, villages, and one large city out of the chaos, known as the Floating City or Citadel of Gith ruled by Zaerith Menyar-Ag-Gith (the Great Githzerai).
 * Limbo was the Astral dominion to which the batrachi retreated in -31500 DR. There, they founded a realm called the Supreme Throne which is also a part of the World Tree cosmology model and even survived the Spellplague.
 * Fennimar was the realm of Fenmarel Mestarine before moving to Arvandor.
 * Tempus Foehammer, Lord of Battles once lived in Limbo. Knight's Rest was the name of his realm which later became its own plane named Warrior's Rest in the World Tree cosmology model.
 * Leira, the Lady of the Mists, once made her home here.
 * Tapann, the patron deity of korreds once made his home here.