The Arcana Realm is the broad term for the many different realms and places governed over by the 22 Major Arcana. They act as a parallel realm to the human realm, accessible to those closely tied to a specific Arcana, or a magician powerful enough to cross the divide.
Each specific realm is dedicated to its ruling Arcana, shaped in a way that aids and compliments its occupant. With a few exceptions, the realms do not change much, or if they do, it is an illusion made by an Arcana themselves.
The Magician's Realm
The Magician's realm is a truly magical place. The part of the realm seen in the game resembles a tropical beach with a dark jungle looming in the distance. The sand is a very deep shade of blue with fluorescent waves crashing on the beach and auroras shining in the magenta night sky. As the apprentice moves further into the realm, they meet fauna that is just as unusual as the realm itself: massive manta rays and giant jellyfish that float effortlessly through the air, and seals with hides dotted with sparkling stars.
The Magician shows how very fluid their realm is when they create an exact replica of the apprentice's shop.
The High Priestess' Realm
The High Priestess' realm is place of eternal night. It consists of small rocky island surrounded by a starry sea where the stars dance above the water. There are stairs carved in the rock of a cliff that lead to the top, where there is a temple of white stone with grand columns etched with glowing symbols. An impossibly large moon hovers over the realm.
It is possible to reach this realm through a personal gateway and a personal connection to the High Priestess herself, as was done by Nadia multiple times throughout her childhood. It may be possible to enter the realm through dreams, as The Devil was able to pull both Nadia and the apprentice to the High Priestess' realm while they slept.
The Hierophant's Realm
The Hierophant's realm is grand, boasting several distinct areas explored in game. The first sight upon entering is the inside of an expansive marble structure, similar to a palace or a temple, decorated in fine details. A painting of the Hierophant adorns part of the ceiling, depicting the Arcana as he's shown in Asra's deck.
A part of this grand structure houses an impossibly large and expansive wine cellar, filled to the ceiling with wines from all over the human realm, many of which are recognizable by Nadia. Another houses a basement, though it acts more as a crypt decorated by the skeletons and tombs of past officials that are embellished in gold. Outside of the building, vast vineyards stretch as far as the eye can see, no doubt part of the source of the Hierophant's wine collection.
The Hanged Man's Realm
The Hanged Man's realm is composed of a thick tangle of mangrove trees, their branches draped with vines and murky water running waist deep. Spherical distortions are scattered throughout the realm, suspended in bubbles playing host to objects frozen in time. It's impossible to keep any coherent sense of direction in the realm. A ribbon of clear water that cuts through the murky water is the closest thing to a path that exits in the realm.
The further into the forest, the darker and heavier the atmosphere. A thick fog creeps between the roots and branches, choking the air. A ring of roots and branches surrounding a clearing is the only place where the air is perfectly clear. A tall, thin lantern lights the clearing. There, the Hanged Man meets his visitors.
The Tower's Realm
The Tower's realm consists of a large, imposing tower of white brick surrounded by an endless, churning sea and horrific storms. A grand spiral staircase curls its way up inside the monolith with no visible or approachable end, entrance, or exit. The tower itself exists in a loop, and no amount of climbing up or down its stairs will allow escape. Even attempting to jump out of the windows spotting the tower's walls, or jumping down the abyss between the staircase does not give freedom, simply putting any escape artists back into the tower.
The only escape from the realm is to accept the Tower's true meaning: great upheaval and disaster that brings about good change. Denying its truth only delays the inevitable, and the Tower has a way of crumbling regardless.
The Devil's Realm
The Devil's realm is vast, consisting of several locations seen in the game. If the apprentice comes invited, the first thing they'll see after stepping through the gate is a great red lake with deadly waters. The way through is on gondola operated by a white stone statue with a smooth, featureless face - one of the Devil's servants. If the apprentice comes uninvited, the land radiates hostility and it is scorched and barren.
Even if there's no sun, the realm is bathed in crimson light. The center of the realm is almost an exact replica of the Vesuvian palace, only instead of white stone and golden spires, it looks like it's carved out of shiny obsidian. The Devil implies it's not exactly what it seems, and that mortals could not truly comprehend the true face of his realm. The throne room is filled with high sweeping arches of obsidian, and at the center of it all looms a black throne on a raised dais.
The Star's Realm
The Star's realm is the beacon of light where the sea meets the sky. More precisely, it's a lighthouse, with the beacon made of thousand little stars, flashing, calling the travelers forward. Beneath the lighthouse there's a labyrinth with walls so tall they block out the sky. The walls of the labyrinth are made of crumbling marble, with statues flanking the great arched entrance. As the path goes further in, the geometry of the place turns stranger, and more unsettling with stairs leading to nowhere and doorways bricked up or dropping off into sudden abyss.
As the apprentice changes by completing the trials of the Star, the labyrinth transforms in response to those changes. If they pass the trials, the labyrinth seems almost peaceful. If they do not, it resists the apprentice every step of the way.