Athas

Athas was a desert planet located in a crystal sphere that was cut off from the rest of the Prime Material plane. Travel to and from the sphere was impossible by physical means and extremely difficult even by magic.

Cosmology
The crystal sphere that contained Athas was not connected to any of the usual spelljamming routes out of Realmspace, Krynnspace, or Greyspace. Its location in the phlogiston was not documented in any book or chart. Some speculated that the crystal sphere was simply too distant from known space, so much so that traveling there would take several lifetimes.

The world's inaccessibility was the result of a property of its crystal sphere that rendered it impenetrable to spelljammers and almost completely cut off from other planes. The border of the Ethereal plane within the sphere was replaced by an environment known as "the Gray", which caused anyone in it to become lost and slowly weaken. It was extremely difficult to overcome by planar travel even by powerful spells such as teleport without error and plane shift, which had a risk of sending the caster into the Gray instead of the intended destination. Even the contact other plane spell had a chance of pulling the caster into the Gray.

One of the few ways of accessing Athas was through Baba Yaga's dancing hut, which traveled all the worlds and planes. In its Hall of Gateways, a portal called the World Gate linked to every world Baba Yaga knew of, including Athas, as well as their respective Shadowfells and Feywilds. This was guarded by a pair of oath wights from Athas, who believed they were defending their world from trespassers. Another mean of achieving this was the powerful planeshifting fortress known as The Planar Sphere, which had one room that became occupied by a group of Athasian halflings after visiting the desert world. Thirdly, the multidimensional World Serpent Inn had among its hallways full of portals a door that opened into Athas, though it was kept under lock and key.

Geography
The majority of Athas was a desert, with most civilization concentrated in a area known as the Tablelands. Beyond nomadic tribes and villages, most of the Athasian races lived within one of seven city-states. Six of these city-states were ruled by tyrants known as the Sorcerer-Kings, powerful arcane spellcasters who made themselves out to be deities or god-like. In place of what was once an ocean of water, the Tablelands were boarded from the east by the Sea of Silt, a great ocean of sand and silt dotted with mudflats, islands, ancient ruins, and horrible creatures adapted to life in the sand, such as sink worms.

History
In The Year of Despair, Malatran calendar, late 14 century DR, a group of heroes of the Living Jungle were sent from the Malatran Plateau through an elemental gate to the far-away world of Athas. Immediately upon arrival, the group was captured by Athasian elf slavers. They eventually managed to escape alongside a young Athasian thri-kreen named Ka'cha when a sink worm attacked the caravan. They went on to return the thri-kreen to his tribe, the Windrunners, then at their instruction traveled to the Ringing Forest for a way back to Toril.

In the late 15 century DR, a book on the history of Athas was part of the collection of the arcanaloth headmaster of the Dweomercore level of Undermountain. The library-fortress Candlekeep also had tomes of lore on Athas, but they were few in number and kept within hidden rooms one had to use ward tokens to teleport into.