The Pale
A colourless, featureless fog that fills the spaces between inhabited continents in a fictional world, and inside which the laws of physics — and, further in, the laws of the mind — stop holding. One reading treats it as the world's own accumulated past, slowly decaying: travellers who pass through absorb stray fragments of memory that are not theirs. It is steadily expanding, with no known limit.
The achromatic, odourless, featureless entropic phenomenon that covers approximately 72% of the world of Elysium — a fog-like field between the inhabited isolas (continents) in which the laws of physics, and at greater distances the laws of psychology, become unreliable. The Pale is the in-fiction analogue of entropy in its broadest metaphysical reading: the transition state of being into nothingness. Its study is called entroponetics.
Etymology§
Pale from English pale in the older sense — pallid, colourless, drained of distinguishing feature — rather than the pale meaning of boundary. The discipline-name entroponetics compounds the Greek entropy with a suffix patterned on scientific-discipline names (genetics, cybernetics).
The Pale is the metaphysical setting of Disco Elysium in a strong sense: the in-fiction physical phenomenon that gives the world its texture of attenuation, loss, and unrecoverability. It is the substance traversed by aerostats (airships) and the substance into which messages, memories, and sometimes whole minds can disappear. Travel through the Pale is physiologically and psychologically dangerous; prolonged exposure causes a blend-over of the self in which the boundary between the traveller and the world's past becomes porous.
The Pale's most distinctive theoretical feature is its relationship with information and memory. One in-fiction theory (advanced by entroponetic scientists encountered in the game) proposes that the Pale consists of past information that is degrading — rarefied past, not rarefied matter. On this reading, the Pale is the accumulated history of the world in a state of slow decomposition; minds that travel through it absorb fragments of memories that do not belong to them. The phenomenon is also expanding at an unknown rate, which gives the worldbuilding its characteristic apocalyptic edge.
The Pale is metaphor and plot device and physics at once — entropy as both literal force in the world and figurative weight on every character's psyche. Kurvitz's 2013 novel had already established the Pale; the game's elaboration extended and deepened it, with the Shivers skill in the game providing the player a direct sensory channel into the kind of perceiving the Pale's proximity demands. Read it as the metaphysical condition the rest of the worldbuilding sits inside.