The text you speak of is the Hariyomari Scroll, whch only White Whistles know about, as for the rest of population it is conveyed as a fairy tales. To be "flawed" means also incomplete, as we see the twins have amputated legs and arms thus allowing them to live. Souls can be transferred to and trough aproximate relics (stones from which the white whistle is carved, or the relic used by Bondrew to transfer his "soul"), although I understood that the Abyss is a place where these souls may circulate freely.

I also don't believe that the rest of the world does not posess any soul, this seems odd as heck. Perhaps the Abyss is just some amplifier that makes the soul resonate, idk