Ectoplasm

Ghosts and other apparently supernatural phenomena are the result of high concentrations of ambient electromagnetic waves in the atmosphere, commonly termed ectoplasm.

Source

All living entities generate ambient electromagnetic waves as a result of bodily functions. The majority of these waves are concentrated in a cluster, located in the ribcage, and involved in the definition of the entity's personality, perception and other facets of their existence. The way each individual manifests these waves is unique, and in layman's terms, this wave signature is called the soul. (Note that the body also generates some other less unique forms of waves - these have more mundane functions such as holding the soul in place and protecting it from being pulled out from the body.)

On death, the electromagnetic waves don't dissipate immediately, but are instead released into the atmosphere. The waves are only termed ectoplasm when they have left the body.

Appearance

Ectoplasm is invisible to most people, and to non-sighted individuals, it can only be detected through its influence on the environment. This is because the electromagnetic waves that comprise ectoplasm usually vibrate at a frequency outside of the visible spectrum. Sighted people are people naturally born with a wider scope of vision and can see them. Technology has been developed to normalise the frequencies within the range of typical human vision, so that other people can see them with special cameras.

To sighted individuals, ectoplasm looks like fire or plasma. Ectoplasm from a single source is always the same colour. Family members of the ectoplasm source tend to have similar ectoplasmic colours as well.

Behaviour

Free-floating ectoplasm, in small amounts, will spread out uniformly and dissipate over time. However, ectoplasm is sensitive to agitation and will tend to cluster, like magnets placed very close to each other.

When stirred by electromagnetic sources, it flows like mist. Ectoplasm is able to pass through most solid objects, but tends to be blocked by objects that have a strong electromagnetic field.

Influence

Experiments have shown that even moderately strong electromagnetic fields can disorient, cause distress in, or even warp the perception of living creatures. Experiments with stronger electromagnetic fields have seen planning, but were aborted due to ethical concerns. Pre-apoc accounts record that contact with unusually strong electromagnetic fields in certain locations around the planet has resulted in mysterious disappearances, irreversible psychological damage to survivors and other unexplained occurrences. Post-apoc, the survivors have grown used to - perhaps evolved to survive in - the heightened strength of the electromagnetic fields, but they are still not immune to its effects, and experience stranger things still.

Ectoplasm in even just moderate concentrations is able to cause hallucinations, and at high concentrations are able to cause changes in or exert a physical influence on the environment. Ghosts with strong enough wills/a strong enough sense of self are able to move objects and resist a weak electromagnetic pull.

Common Phenomena

Eddies

Eddies are small swirls and ripples in the ectoplasmic mist that envelopes everything. The ectoplasmic concentration in these clusters is very low. These are fairly common on the way to the generator funnel, and commonly manifest as "unexplainable" phenomena (e.g. cryptid sightings), without a particular "main" entity. They may or may not dissipate on their own.

Ghosts

Ghosts are the clusters of ectoplasm released from living entities. They are single entities, and if fresh from the source, are usually harmless and can be communicated with. Some may linger for years after their death, if their will is strong enough, and if there are obstacles in their path to the funnel. However, the longer they remain, the greater the risk of corruption into Strays. Revenants are typically recruited as fresh ghosts, when they are most stable.

Strays

Strays are ghosts that have destabilised over time. They may have merged with ectoplasm in the atmosphere causing impurities in their colour, and/or lost parts of their ectoplasmic mass. These can be considerably more dangerous, having lost parts of the memory or gained multiple consciousnesses, and gained the ability to exert an influence on the environment (intentionally or otherwise). Some eventually will collapse into ectoplasmic mist, but Revenants are typically mobilised to break them up.

Spectres

Spectres appear similar to ghosts and Strays, in that there appears to be a central entity, but they are larger versions of eddies, and accordingly are accompanied by bigger environmental changes. Unlike Strays, they have a more uniformly patchwork composition of soul matter from different sources, and do not have enough of a single soul to have much of a consciousness. The core entity may appear sentient, but this is an illusion. These form the majority of cases and can pose a major danger if not thoroughly broken up by Revenants.