Astral Space is the non-corporeal regions — the Realms Invisible — of the Mage cosmology, defined by the minds, ideas, thoughts, and emotions of beings within the Fallen World. It may have at one point contained, included, or bordered upon the Supernal Realms, although it is now separated from them by the Abyss. It contains three main Astral Stratum, or levels: The Oneiros, which is a unique reflection of every person's mind, the Temenos, a reflection of the minds of all mankind, and the Anima Mundi, which is a reflection of ideal forms and essences of the natural world.
The Mastigos, through their mastery over the Arcanum of Mind, are the Path who deal the most with this realm.
Reaching Astral Space
To reach Astral Space, a mage must pass through though his or her Astral Threshold. This requires entering a state of meditative lucid dreaming. The Astral Threshold is generally some emotional or psychological concern or strain on the mage that manifests as an obstacle that must be overcome by spending mana. Then, the obstacle sets the tone for the rest of the journey by setting a path that the mage must follow. For example, if the mage's obstacle was one of drowning, the rest of his path will likely be underwater. By progressively travelling deeper, the traveller can access deeper Astral Strata, starting with the Oneiros, then the Temenos, and finally the Anima Mundi.
The Oneiros
The Oneiros is the first Astral Stratum and is unique to each person. Approaching it on the Astral Path gives a mage a sensation of being too close to an uncomfortable truth about themselves. Despite what many mages intially believe, each Onerios is not a planet unto itself but a series of collected scenes and disparate locations that embodies each person's memories, fears, Vices, and personality aspects.
The Temenos
The Temenos is the realm of "Physicalized Abstractions," which mirrors the collective unconsciousness of mankind. Approaching it on the Astral Path gives a mage a sensation of being pointedly ignored by many people.
The Primordial Dream of the Begotten is part of the Temenos; Beasts refer to the rest of the realm as the Bright Dream.
The Anima Mundi
The Anima Mundi is the world soul, containing the idealizations of the natural world and of mankind's impact upon it, as well as the farthest borders of the Fallen World, where remnants of the Supernal Realms lie. Approaching it on the Astral Path causes a sensation of vast age and size that makes a mage feel small in comparison. Bordering on the Abyss, it is not possible for a mage to pass any farther on an Astral Journey since it is the deepest Astral Stratum
The Anima Mundi is a bizarre and sometimes alien place. Mages who travel there may use an amnion to protect themselves from becoming subsumed by the things they see.