souls are the spiritual component of physical things, and this extends to even non-living things (places, objects and lifeforms all have souls) pretty much everything that exists has a soul. These souls are are often on the same side of the spiritual war as the otherworlders but not always although when they allign with the jotunn its almost always because the jotunn tricked them because what the jotunn want is not in the best interest of souls
unlike otherworlders souls come from the spiritual manifestation of physical objects, when something is created it has a soul but that soul didn't exist before that thing existed, however the soul of something can sometimes persist after the thing is destroyed
when it comes to living things souls are passed down through generations and living things can reincarnate as their own descendants after they die
souls can be converted into jotunn by the primordial and the primordial plans to do this as souls will eventually become gods themselves when this universe comes to an end they will rival the primordial so making them into jotunn beforehand would make them slaves to thier nature and subserviant to the primordial so the primordial will keep its control over reality even as the universe reproduces itself, jotunn are slaves to thier nature and dont have free will while souls do have free will
the primordial was once the soul of something that existed in a universe that existed before ours and the otherworlders had to steal the god-like power from the primordial to create our universe because the universe the primordial wanted to create was a world without free will so that the primordial's power would never be challenged, and the primrodial wants to destroy our universe and remake the universe how they want it