There is four types of souls any living being has. They can have a soul that is pure light filled with kindness and love. There is the soul of light that has a dark spot. A ability to sin and cause trouble but never at a disturbing level. Kindness and love still prevail in this soul. Then there is a sould of full darkness. A soul like the dark night without stairs. A emptiness of not being able to love is a now filled with hate. There is no exscape from this massacure in a bodily form. Nothing can stop the bloodshead the dark souled creature causes on others.
Then there is a soul of the darkness that has a small light. A small star barely surviving in an endless black hole of rage and dispair. The broken, barely breathing hope in Pandora's box.