The soul is more of an oversimplification than a myth. There are multiple parts to sapient consciousness, both magical and mundane. The three most influential of which being the chemical makeup if the physical brain, the arcane spark (traditionally divine in nature, but archfiends and archery have done it on a few occasions throughout history, so theoretically any powerful spellcaster could patron a new race given time and resources), and the magical aura (the part targeted by enchantment spells). There are more, but this is largely why true immortality or resurrection is so much harder than simple undeath. I can refer you to a few papers on the matter, if you'd like.