Kel Valhaal, Reign Array, The Genesis Caul and Ololon are four faculties of the soul. The first pair is active, the second pair is passive. They join together as an assemblage, which is called YLYLCYN. All of this is contingent. Why these four faculties and not others? Only because that's how it is for now - basically for evolutionary reasons. There could be new faculties in the future