Secret worlds and invisible domains surround the world of the Dungeons & Dragons game. Godly dominions, elemental chaos, shadow kingdoms, and faerie realms are all part of the world. Most mortals know little of these things, but heroes are a different matter. Heroes often find that adventure calls them to distant and strange dimensions indeed.

The Feywild

The closest of these alternate worlds is the Feywild, or the realm of faerie. It is an “echo” of the mortal world, a parallel dimension in which the natural features of the lands and seas are arranged in much the same configuration. If a mountain stands in a given place in the mortal world, a similar mountain stands in a corresponding place in the Feywild. However, the Feywild is not an exact reproduction. Built structures and terrains are not copied in the faerie realm, so a valley dotted with farm fields and towns in the mortal world would simply exist as untouched, unsettled woodland in the Feywild.

The Feywild’s many vistas can catch your breath with beauty, but the Feywild is far from safe. Heroes visiting to Feywild might encounter:

• A mossy forest glade where evil druids spill the blood of hapless travelers over the roots of the thirsting trees;
• The tower of an eladrin enchanter;
• A fomorian king’s castle in the dim, splendid caverns of the faerie Underdark; or
• A maze of thorns in which dryad briarwitches guard an evil relic.

The Shadowfell

Just as the Feywild is an echo of the natural world, so is the Shadowfell. However, the Shadowfell mimics the mortal world in a different manner. The Shadowfell is the land of the dead, where the spirits of the deceased linger for a time in a dark reflection of their previous lives before silently fading beyond all ken. Some undead creatures are born in the Shadowfell, and other undead are bound to it, but some living beings dwell in this benighted realm.

Like the Feywild, the Shadowfell also reflects the mortal world imperfectly. Towns, castles, roads, and other objects built by mortal kind exist in the Shadowfell about where they should be, but they are twisted, ruined caricatures. The shadowy echo of a thriving seaport in the mortal world might be a dilapidated, desolate port whose harbor is cluttered with the rotting hulks of shipwrecks and whose busy wharves are empty except for a few silent and furtive passersby. In the Shadowfell, heroes might venture into:

• A necromancer’s tower;
• The sinister castle of a shadar-kai lord, surrounded by a forest of black thorns;
• A ruined city swept by long-ago plague and madness; or
• The mist-shrouded winter realm of Letherna, where the fearsome Raven Queen rules over a kingdom of ghosts.

The Elemental Chaos

All of the cosmos is not tied to the mortal world as closely as the Feywild or Shadowfell. The natural world was created from the infinite expanse of the Elemental Chaos (or Tempest, or Maelstrom), a place where all fundamental matter and energy seethes. Floating continents of earth, rivers of fire, ice-choked oceans, and vast cyclones of churning clouds and lightning collide in the elemental plane.

Powerful beings tame vast portions of the chaos and shape it to their own desires. Here the efreeti City of Brass stands amid a desert of burning sand illuminated by searing rivers of fire falling through the sky. In other places in the Elemental Chaos, mighty mortal wizards or would-be demigods have erected secret refuges or tamed the living elements to build their domains.

Elemental creatures of all kinds live and move through the Elemental Chaos: ice archons, magma hurlers, thunderbirds, and salamanders. The most dangerous inhabitants are the demons. In the nadir of this realm lies the foul Abyss, the font of evil and corruption from which demonkind springs. The Abyss is unthinkably vast—thousands of miles in extent—and in its maw swirl hundreds of demonic domains, elemental islands, or continents sculpted to suit the tastes of one demon lord or another. Within the Elemental Chaos, heroes might explore:

• The crystalline tower of a long-dead archmage;
• A grim fortress monastery of githzerai adepts;
• The diseased Abyssal continent where Demogorgon rules amid ruined temples and bloodthirsty jungle beasts; or
• A vast polar sea lit only by the cold glitter of icebergs and flickering auroras, in which the frozen stronghold of a frost giant warlock lies hidden.

The Astral Sea

One final extradimensional realm touches on the mortal world: the Astral Sea. If the Elemental Chaos is the manifestation of physicality, the Astral Sea is a domain of the soul and mind. The divine realms, the dominions of the gods, drift within Astral Sea’s unlimited silver deeps. Some of these are realms of glory and splendor—the golden peak of Mount Celestia, the verdant forests of Arvandor…. Others belong to dark powers, such as the Nine Hells where Asmodeus governs his infernal kingdom. A few astral dominions lie abandoned, the ruined heavens and hells of gods and powers that have fallen.

Only the mightiest of heroes dare venture into the dominions of the gods themselves. In the Astral Sea, heroes may find:

• The iron city of Dis, where the devil Dispater rules over a domain of misery and punishment in the second of the Nine Hells;
• An artifact guarded by race of cursed warriors whose castle of adamantine overlooks the war-torn plains of Acheron;
• The black tower of Vecna, hidden in the depths of Pandemonium; or
• A dragon-guarded githyanki fortress, drifting through the silver sea.

No one is knows how many astral dominions there are. Some dominions, such as the Nine Hells, are the size of worlds. Others are no larger than cities, rising like shining islets from the Astral Sea. Several dominions have been ruined or abandoned, usually because the gods who made them were destroyed or forgotten. What sorts of treasures—or perils—might slumber in such places, only learned sages could say.

Overal I really like the sound of this.

The shadar-kai are a race of shadow-fey warriors.

Fiend folio 3rd edition or something like that.