>>718625110 (OP)
I want my setting to be a bunch of fantasy things explained as sci-fi phenomena.
>Souls
Brains that have evolved from matter to energy
>Magic
The souls channeling a part of their energy into various states
>Ghosts
A soul that managed to stay coherent after the death of the body despite usually dissipating on death.
>Restless ghosts
The most common way for a soul to persist is "unfinished business". An instinctive defense mechanism triggers in a soul that is convinced it's not supposed to die yet, making it maintain its coherence outside of its body in an attempt to finish some important task it's convinced it needs to finish. Protecting loved ones, reporting a severe crime, revenge killings, etc.
>Haunting
A phenomenon of a restless ghost squatting in a property of its choice.
>Paranormal phenomena
Since "Magic" comes from the soul, a ghost is able to do very weak and rudimentary forms of magic. Rising/falling temperatures are thermal magic. Objects getting thrown around are telekinesis, etc.
>Exorcism
There is "placebo" exorcism like religious symbols, prayers, rituals, incense, other bullshit, that only works if the ghost believes it works (Oh fuck, he's calling jebus on my ass, I gotta get the fuck out of here!). Should you attempt to shove a cross in the face of some atheist redditor's ghost - he will only obnoxiously laugh in your face. Proper exorcism is done by people with experience in arcane studies, ones that know how to destabilize and dissipate volatile arcane energy.
>Possession
An attempt by a soul to sever another soul's neural connection to its body and hijack control over it.
>Reincarnation
A successful possession of a fetus.
Etc