There are many types of phenomenon, beings, and places, each of which interact with each other in slightly different ways. This guide is here to help you understand many of the terms that recur throughout the project.
Goodbye Strangers begins in the familiar world.
we live here...
You are here right now.
Then, it explains what the strangers are, and introduces the space in which they dwell.
Strangers are a natural phenomenon that take on composite, human-like behaviours. Though they show up in cities, they remain unseen by most people, existing within their own, interwoven layer of this world's physical reality.

Created by the friction between this and other dimensions, strangers can only exist as a by-product of human thought, and every factor that influences their form is a reflection of this. Even when they seem to imitate animals, they only reflect a human's perception of the thing. Strangers have more in common with a plastic flower than a real one, and are more like cat costumes than cats.

Although the strangers exhibit complex behaviours and exert both physical and mental influence upon the world, they do not have thoughts. They do not have feelings. They do not have a thoughtform.x They cannot be communicated with. They are not alive.
x A thoughtform is the part of the living being that perceives, senses, and decides – in short, it is equivalent to what is typically known as "consciousness" or "free will".
...and they are there
Strangers dwell in a thin sub-dimension that exists on top of and as part of our world. Its connection to physical space ebbs and flows. When the space is undisturbed by people, this dimension settles against our own, allowing physical contact with our world.

The dimension remains unobservable, shifting away from our physical reality long before the space can be interrupted. It is this entanglement and detachment that allows the strangers to generate and propagate unobserved.
Then, it introduces the sensitives.
A sensitive is a person who can enter into strange space to engage with the phenomenal shapes known as strangers.
A dissembler is a type of sensitive that can make a stranger inertx through skin-to-skin contact. An inert stranger cannot move, nor can it inflict its effects and influences upon the world. Dissemblers are furthermore almost completely untouched by the effects, both positive and negative, of free roaming strangers.
x. These prostrate strangers mirroring the extruded drones of the V.H.Z. era.
A laminate is a type of sensitive whose physical touch can retrieve dead stranger matter from strange space. Parts that bear resemblance to the stranger's form are less likely to survive the transition – fluids and tissues have far greater odds than heads or limbs, while a fully intact corpse would be virtually impossible to recover.
An eraser is a type of sensitive whose presence physically repels strangers, even to the point of damage to the stranger. Consequently, an eraser cannot physically touch a stranger, except those rendered inert through various means.
A projector is a type of sensitive that can bring a stranger out of strange space, as long as the stranger's physical form remains unseenx by a non-sensitive. In this way, they can displace a stranger's effects, channeling them into the familiar world.
x Should a stranger's form be revealed, a phenomenon known as a "blink" occurs. With a scramble of light and colors, the stranger's body is removed, and all non-senstives human experience anything from light nausea to momentary vertigo, but always with total loss of memory of the event, and some degree of disorientation.
But, being a sensitive is not the only way that someone can be different.
A psychic is a person who possessses bifurcate thoughtforms, allowing them to enter adjacent dimensions. They have unusual biology, including a cluster of nerves known as the messianic crown that grants them their abilities, as well as psychoactive tears.

Psychics are able to see strangers at all times, regardless of whether or not the connection to strange space is interrupted. To a psychic, a stranger is perceived as either a holographic version of itself (when the connection is interrupted) or its physical form (when the connection is not). Regardless, a psychic cannot touch a stranger, with any overlap of their physical forms removing the stranger from reality.
A blank is a person born without a thoughtform, with such an exceedingly rare event occuring only in the case of interference by outside forces.
An empty is a person who has lost their thoughtform.
And some people are not so different at all.
A standard does not have an appreciably unique internal or external experience. They are "normal", and possess a normal thoughtform.
Within the story, there are also worlds beyond our dimension, as well – such as the infinitely powerful Hells.x
xHells are powerful dimensions that are adjacent to our own. Although they cannot be physically visited, nor can their internal structure be readily inferred, their hell fields influence various structures, interactions, and properties.
Blue Hell
Blue Hell is a dimension that projects blue hell fields. It resonates with certain types of strangers, causing them to produce psycholyx as a byproduct of this resonance.

Blue Hell shares its shape with dissociative episodes, and the loss of the self. The ego is erased, and the outside world pours in. Its edges are hard, and monochromatic.
xPsycholy (or, 最己離) is a blue liquid that acts as a powerful hallucinogen, incuding effects that are euphoric, kaleidoscopic, and long-lasting, with chronic users growing more and more detached from reality with every trip.
Red Hell
Red Hell is a dimension that projects red hell fields. It resonates with certain types of strangers, inducing the production of Red Milk.x

Red Hell shares its shape with psychotic episodes, and the muddling of the self. The ego boundaries become diffuse, bleeding in and out freely with the outside world, like dye on a page dipped in water.
xRed Milk is a white and red liquid that causes a fevered rush of energy and a loss of inhibitions. This can manifest as desperate ecstasy, or violent rage, depending on the user's state.
The Flood
The Flood is the break that occurs when the structure and order of one world can no longer be sustained. It marks the end, and cannot be resisted.
A medium is a person who has the capacity to see ghosts.
A ghost has a thoughtform, but no body. All human beings with thoughtforms start off as ghosts.