A Brief Guide to the Known Planes:
A city at the “Center” of the Mutliverse. Oddly set in the shape of a torus the only way in or out of Sigil is by using one of the many portals that dot the city. With the proper key (a flower, a hand gesture, a magic word etc.) every door, window, or opening lets a traveler out in some corner of the multiverse. You just need to know which one. It was once ruled by the Factions under the auspicies of the Lady of Pain, a mysterious figure of terrible power. The Lady of Pain has since excised the Factions to the farthest reaches of the multiverse, yet they are schemeing to retake power. The Boathouse is here in the Market Ward.
The Mortal World
Where clueless mortals live. They tell Ghost Stories and Fairy tales, say you better be good or you’ll wind up as Asmodeus’ door stopper, and bury the dead in sacred ground so that Demons can’t steal souls. But they don’t know the real dark of the multiverse.
The Astral Sea
Home of the Gods and their servants, populated mostly by Angels and Devils. Other notable races include the Githyanki pirates, Shardmind psychics, Devas and Tieflings who seek knowledge of their origins. Also the Maruts and the Couatls.
Celestia: Dominion of the Gods Bahamut, Moradin, and Kord. Millitaristic Gods of Good who are preparing for a war with the Demons of the Abyss
Hestavar: Dominion of the Gods Pelor, Ioun, and Erathis. Gods of well ordered and peaceful society, in the process of rebuilding the lattice of heaven to restore order to the multiverse.
Arvandor: Dominion of the Gods Corellon and Sehanine, former Archfey who were raised to God status after the first war of the Gods. A wild paradise for souls who worship freedom beauty and love above all things.
Tu’Narath: Capital of the Githyanki Raiders
Carceri: Prison of Gods most vicious enemies
The Nine Hells: Where damned souls forbidden from entering the Dominions are cast for eternal torment. Ruled by the Greatest of Devils, Asmodeus.
A sprawling land of magic and wilderness. Home to the Fey Courts, who remain neutral in Planar conflict but contain vast resources of magical knowledge and networks of spies that every Devil and Agent of Good wants to get their hands on.
Where souls go before being sent to their final judgement. Ruled by the Raven Queen, a human sorceress who slew Nerull, the God of death and now judges the souls of the dead from her temple in the dark mountains of Letherna. She is served by her Shadar-Kai, barbaric yet stoic humans who have turned themselves over to a cult of pain to remember their mortal lives, and the Revenants, souls of the dead she has brought back from the void for mysterious purposes. Demons of the Abyss wander the Shadowfell searching for souls that did not receive proper burial they can press-gang into their war against the Astral Sea.
Gloomwrought: The major port of ships passing through the Plane of Shadows.
The Elemental Chaos
A roiling mass of matter and energy from whence the Mortal World was created before it passed into control of the Gods. Once ruled by the Primordials, they now lay in chains under mountains of ice and fire. Their servants the Titans now struggle against the Genies for control of the Plane. The Githzerai, a cousin race of the Githyanki, are also quite populous here. Unlike the Astral Gith who are vicious and warlike, the Githzerai are monastic and peaceful, yet compotent warriors to defend their monasteries.
The City of Brass: The Greatest City of the Elemental Chaos, a trading port of the Fire Genies known as the Efreet.
Zerthadlun: The largest monastery of the Githzerai.
The Abyss: A swirling portal into the heart of pure evil, where primordials are transformed into Demon Princes, ready to one day march with their Demons across the Elemental Chaos and to destroy the Dominions of the Astral Sea.