[@Fabulous Knight] Well, as I described it for now: when a body holding a soul dies, the soul shatteres into fragments named spirits. These spirits return to Reathos' Primordial Pool.

From that point things seem to be a little foggy so I suggest we stamp it out for real. Either Slough can drain (for some odd reason) from the spirits in the Primordial Pool (which serve as building blocks for souls) and makes new ones. Or the Primordial Pool makes souls out of itself and releases them into the wild World.

Personally I'd go for idea 1.