Known Multiverse

The Multiverse is vast, possibly infinite. But a number of its constituent Planes are known if not understood.

Inner Planes
The Inner Planes are the closest and most similar to the Material Plane. The Inner Planes interact somewhat freely with each other, sometimes at random, and are reachable from each other without significant arcane power.

Artio, the Material Plane
Artio, also known as the Material Plane, is the centre of the Known Multiverse. It is the Plane to which all other Planes are compared. It is unaligned to any of the Great Powers as a whole but nearly every Great Power has representatives and followers on this Plane.

Feywild
The Feywild, also known as the plane of Faerie, exists as an "echo" or Sister of Artio. It was from here that the fey originated, giving the Feywild its name, and it is also a place of unusually potent magic.

Shadowfell
The Shadowfell, also known as the Plane of Shadow, is one of the Sisters of Artio. It is the dark shadow of Artio and is the place where all souls from Artio must pass to reach their afterlife. Other names for this plane included Shadowland and simply Shadow. It is ruled by The Raven Queen.

Plane of Air
The Plane of Air is a realm of change and howling winds. Amongst this near constant chaos a centre of order, the City of Aaqa, home of the Wind Dukes, stands vigil.

Plane of Earth
The Plane of Earth is a realm of stability and rigid mountains. The largest cavern beneath these mountains is the capital city of the Dao, the City of Jewels.

Plane of Fire
The Plane of Fire is a realm of passion, change, and burning wastes. At its centre is the City of Brass, the most famous and powerful city in the Elemental Planes.

Plane of Water
The Plane of Water is a realm of constant tides and flowing water. It is ruled from the Citadel of Ten Thousand Pearls.

Outer Planes
The Outer Planes are similar enough to Artio for mortals to traverse without being instantly destroyed but are neither easily reachable from Artio nor likely to interact with the Inner Planes on their own. It is believed that the Outer Planes are the source of Cosmological Morality as its sixteen planes rigidly align to the Eight Alignments.

The Outer Planes can be pictured as a great wheel, with The Paths winding between all layers. Each Plane partially reflects and is reflected by two others, in a manner similar to the Three Sisters or the Elemental Planes, and are considered to be bordering each other.

The Paths
The Paths connect from the Shadowfell, and a few other places on the Inner Planes, to the Outer Planes. The Paths connect to the Fortress of Memories in the Shadowfell and are guarded by The Raven Queen herself. The other connections to the Inner Planes are almost invariably guarded by powerful fiends and angels.

The River Styx
The River Styx is an oil slicked river full of foul flotsam and its shores dotted with the fetid remains of past battles and atrocities. It connects to the Evil Outer Planes. Damned souls, or the truly unfortunate, who find themselves in the River Styx are swept away to the feeble mercies of the evil aligned Great Powers.

The Infinite Staircase
The Infinite Staircase appears as a nondescript staircase that changes as one ascends. It connects to every one of the Outer Planes but not every entrance to the staircase leads to every Plane. If one accidentally encounters stumbles upon an Infinite Staircase there is an equal chance that one will emerge in any one of the Planes.

The Upper Planes
The good aligned Great Powers rule the Upper Planes.

The Seven Heavens of Mount Celestia
The single sacred mountain of Mount Celestia rises from a shining Silver Sea to heights barely visible and utterly incomprehensible, with seven plateaus marking its seven heavenly layers. It is ruled by the Great Power known as the Celestial Triumvirate. There is some debate as to whether this plane should be known as the "Eight Heavens of Mount Celestia" with the capture and inclusion of the Iron City.

It borders Bytopia and Arcadia.

Its alignment is Lawful Good.

The Twin Paradises of Bytopia
The two layers of the Twin Paradises of Bytopia are similar yet opposite: one is a tamed pastoral landscape and the other an untamed wilderness, yet both reflect the plane's goodness and it's acceptance of law and order when necessary. It was ruled by the Great Power known as the Lords of the Golden Hills before the Great Sundering. It currently has no ruler.

It borders Celestia and Elysium.

Its alignment is both Lawful Good and Neutral Good.

The Blessed Fields of Elysium
Elysium is home to creatures of unfettered kindness and compassion, and a welcome refuge for planar travellers seeking a safe haven. The Plane's bucolic landscapes glimmer with life and beauty in their prime. It was ruled by the Great Power known as the Keeper's of the True Grove before the Great Sundering. It currently has no ruler.

It borders Bytopia and The Beastlands.

Its alignment is Neutral Good.

The Wilderness of the Beastlands
The Beastlands is a plane of nature unbound, of forests ranging from moss-hung mangroves to snow-laden pines, of thick jungles where the branches are woven so tight that no light penetrates, of vast plains where grains and wildflowers wave in the wind with vibrant life. It was ruled by the Great Power known as the Wild Hunt before the Great Sundering. It currently has no ruler.

It borders Elysium and Arborea.

It's alignment is both Neutral Good and Chaotic Good.

The Olympian Glades of Arborea
Larger than life, Arborea is a place of violent moods and deep affections, of which backed by steel, and of passions that blaze brightly until they burn out. Its good-natured inhabitants are dedicated to fighting evil, but their reckless emotions sometimes break free with devastating consequences. Rage is as common and as honoured as joy in Arborea. It was ruled by the Great Power known as the Seldarine before the Great Sundering. It appears to have recently gained a ruler, but their identity is currently unknown.

It borders the Beastlands and Ysgard.

It's alignment is Chaotic Good.

The Heroic Domains of Ysgard
Ysgard is a rugged realm of soaring mountains, deep fjords, and windswept battlefields, with summers that are long and hot, and winters that are wickedly cold and unforgiving. Its continents float above oceans of volcanic rock, below which are icy caverns so enormous as to hold entire kingdoms of giants, humans, dwarves, gnomes, and other beings. It was ruled by the Great Power known as the Ordning before the Great Sundering. It currently has no single ruler.

It borders Arborea and Limbo.

Its alignment is Chaotic Good and Chaotic Neutral.

The Middle Planes
The Middle Planes are connected to the other Outer Planes but are not directly ruled by any of the Great Powers. They each exist at opposite sides of the theoretical Outer Planes wheel.

The Ever-Changing Chaos of Limbo
Limbo is a plane of pure chaos, a roiling soup of impermanent matter and energy. Stone melts into water that freezes into metal, then turns into diamond that burns up into smoke that becomes snow, and on and on in and endless unpredictable process of change.

It borders Ysgard and Pandemonium.

Its alignment is Chaotic Neutral.

The Clockwork Nirvana of Mechanus
On Mechanus, law is reflected in a realm of clockwork gears, all interlocked and turning according to their measure. The cogs seem to be engaged in a calculation so vast that no deity can fathom its purpose. A god-like being known as Primus rules here, but as their interest does not extend beyond their own borders they cannot be considered a Great Power.

It borders Arcadia and Acheron.

Its alignment is Lawful Neutral.

The Lower Planes
The evil aligned Great Powers rule the Lower Planes.

The Windswept Depths of Pandemonium
Pandemonium is a plane of madness, a great mass of rock riddled with tunnels carved by howling winds. It is cold, noisy, and dark, with no natural light.

The Infinite Layers of the Abyss
The Abyss embodies all that is perverse, gruesome, and chaotic. Its endless layers spiral downward into ever more appalling forms. Each layer of the Abyss boasts its own horrific environment. No two layers are alike.

The Tarterian Depths of Carceri
The model for all prisons in existence, Carceri is a plane of desolation and despair.

The Grey Waste of Hades
A grey land with an ashen sky, Hades is the destination of many souls that are unclaimed by the gods of the Upper Planes or the fiendish rulers of the Lower Planes.

The Bleak Eternity of Gehenna
Gehenna is the plane of suspicion and greed. It is the birthplace of the yugoloths, which dwell here in great numbers.

The Nine Hells of Baator
The Nine Hells inflame the imaginations of travellers, the greed of treasure seekers, and the battle fury of all mortal creatures. It is the ultimate plane of law and evil and epitome of premeditated cruelty.

It was recently conquered by the forces of the Celestial Triumvirate.

The Infinite Battlefield of Acheron
Acheron has four layers, each made of enormous iron cubes floating in an airy void. Sometimes the cubes collide. Echos of past collisions linger throughout the plane, mingling with the sounds of armies colliding. That's the nature of Acheron: strife and war.

It was recently conquered by the forces of the Celestrial Triumvirate.