The Dreamings

Nearly every sentient creature departs their world daily, their mind whisked away into a different plane parallel to the material when they sleep. Known by many names, the Dreamings, the Dreamlands, the Realms of Thought, and more. The Dreamings are divided in two versions, called by scholars the Twilight Dream and the Dark Dream. In dreams, the mind has powerful sway over the reality it finds itself in, conjuring images, emotions, people, and experiences sometimes out of thin air or out of past experiences, drawing on a frame work to create a new story. Most often this is done unconsciously, and the Dreaming looks little different from the waking world, but awareness of differences can be noticed by lucid dreamers or physical visitors who transport themselves across the planes.  Because the Dreamings are built of the stuff of imagination and the mind, it is malleable to unconscious dreamers, and completely morphic to lucid dreamers and visitors, allowing flight, impossible strength, or shapechanging at a thought while in the scape.
The Dreamings are twin sides of the same coin, reflections of the Material Plane. There is no control over which dreamscape one ends up in, but many more nights are spent in the Twilight than the Dark Dream. The Twilight Dream consists of positive emotions, manifestations of light, love, success, joy, and freedom. Most dreams come to the Twilight, where the brain can bathe itself in positive emotions and experiments, free to do what it wishes. Sadly, the vast majority of the time, after visiting the Twilight, the time spent their is forgotten, the experiences plunging into the deepest parts of one's subconscious. The Dark Dream is a negative place, a realm where nightmares happen. Fears, worries, and anxieties appear, at best to exercise the mind for real life concerns, at worst to torture the dreamer. Pulling yourself out of the Dark Dream can leave you paralyzed in your bed for an extended period, and lucid dreamers and physical visitors are often purposefully attacked by the denizens of the realm.
Despite the land being easily changed by foreigners, the planes are very much teeming with life all its own, though they cannot interact nor see the unconscious dreamer's creations. In both, creatures of myth and fairy tale are alive and well, living lives of fable. Fairies are prolific in the Twilight, living lives of eternity dancing in the perpetual fading light, amusing themselves with stories, pranks, and artistic expression. They are entirely alien from material creatures, and when the Twilight Dream leaks into the World, their strange way of life baffles the inhabitants of the World, and is the source of the fairy tales spread throughout all cultures. Interestingly, the manifestations of seasons rule the Fey Realm, a creature distantly similar to elves known as the eladrin.
The Dark Dream is a place of misery manifest. Cruelty implies conscious desire to do so, and as such is reserved only for the Lower Planes in the Astral Sea, leaving the creatures of unwitting sorrow to live in the Dark. Manifestations of our worst emotions walk the plane, as well as beings of terrifying fables. Undead are most common here, bumping shoulders with monsters, such as the catoblepas, siren, manticore, banderhobb, and scarecrow. Witches and hags are also residents, and dreamers are often lured into their lairs on this plane. A creature found nowhere else are called the sorrowsworn, pathetic creatures that are the remains of miserable dreams after the dreamer forcibly tears themselves from the plane. Of note, night hags are fiends that may travel to the Dark at will and spend the majority of their time here, and their Nightmare Haunting forces a dreamer into the Dark with her.

Manifestation

The Twilight Dream is a copy of the material world, bathed in perpetual setting sunlight, a wild and colorful landscape of exaggeration and parody. A town in the material will appear in the dreamland as a town with strangely sized buildings, curved and sloped at weird angles, the central fountain raining a rainbow of light where the subconscious lovers finally come together. More often than not the sun and sky cannot be seen, due to the immense canopy of forest that makes the majority of Faerie. The changes brought by dreamers are only visual by the individual, and do not permanently change the visualization of the worldly reflection.
The Dark Dream is the bleak shadow of the Material World, where a town in the waking world appears shaded and suspicious, the inhabitants dower and unfriendly. The buildings lean in, the forests are dark, and the deserts and mountains exaggerated and hateful. The sky is a black starless moonless night, with a perpetual black sun ringed by a halo of cold white that gives neither light nor warmth to the land below. Forests and towns crawl with hungry eyes, watching and hunting a dreamer's paranoia. Deserts appear as cracked plains of waving jagged rock. Mountains climb many times taller than normal, wrought of darkened rock, sharpened and sheer, impossibly high and steep. Rain falls cloudlessly salty as tears, burning like a fresh heartbreak.

Localization

Despite being foreign and parallel reflections of the Material World, sometimes the Dreamings bleed over into the waking world. In a dense magical forest, perhaps a manifestation of the Twilight may emerge, allowing a faerie kingdom to spawn, and the myths to walk among the material. A story may tell that you may not cross a field at night, for you will not leave that field until daybreak, but this same field is easily surmountable during the day. Such an example would be a manifestation of the Dreamings. It is impossible to predict where a manifestation may appear, and how long it will remain, and how easy it might be to cross back and forth.
Portals can be conjured by sufficiently powerful mages that allow instant travel back and forth into the plains, with portals to the Twilight appearing as a light gold, acting like a prism from certain angles. Dark portals appear gloomy and colorless, a neutral tone of greys.

Type

Metaphysical, Supernatural