The Soul is the means by which Sophont may cast spells. It an identifiable and quantifiable energy signature which began with the Verin, was birthed into the Sazashi, and which some Sazashi brought to humanity when Aempis occupied earth.
It allows use of the Meta so that Sophont may cast spells. According to most faithful it is also a link to the afterlife. To have your meta damaged or removed, no matter how temporary, is to risk losing access to the afterlife.
The soul is a conduit for your will made manifest. It connects you to the beyond, the within, and the without.
Gaining a Soul
A soul develops when an observing, soul-bearing entity spends time in close proximity of a soulless entity who possesses higher reasoning and willpower, and a has a sense of identity. The amount of time it takes depends on the duration and intensity of these capabilities of the observer's emotions.
The development of a soul is the metric by which Sophonce was first marked and later defined.
Losing a Soul
Being exposed to a Null Void for a great duration or being the target of Meta Immolation can temporarily dispel the soul. This has no major effect on the Sophont, but will usually leave them slightly despondent. Re-entering a region with Meta and interacting with another being with a Soul will quickly kickstart whatever process causes the Soul to regenerate, and they will be fine in no time.
This condition is known as Hollow Heart or Null Sickness.
Most Sophont develop a soul early into puberty—around 9-11 years for most. Some develop it sooner or later depending on life circumstances, such as hardship or fortune, and there are rare cases where developmental issues have hindered or hurried the development of a soul as well.
In most societies, Naissance is a coming of age which grants validity to their voice. Unfortunately, there is historical precedents for societies which see the young as expendable due to a lack of Soul.
Like the flaking of skin and the silent discarding of hairs, Echoes are what the soul leaves behind. When you laugh, your joy hangs in the air like smoke. When you cry, the stain of your sorrow lingers beyond the drying of tears. It's rare to see Echoes with your bare eyes, and indicative of great danger when you can, but they are all around you.
Do not engage a Manifestation.
If a Manifestation speaks your name, find a temple immediately.
There are few benefits for society to allowing these stray emotions to build up. Successful and healthy cities maintain a force of hired and automated Exorcists to serve as psychic janitors—breaking echoes down into harmless Pasteurized Meta.
An excess of ambiant sorrow can fill the mind with grim and troubling intrusive thoughts, though a moderate amount is often accepted in places of grief, such as tombs.
Just as excess sorrow can engender a sense of doom even when in comfort, too much joy can leave a population complacent and happy even in the midst of brutality.