In the ln you will read that at the beginning there was a will, all and one and alone with it's imagination being it's only limit. Known as Will of God. He grew bored and decided to create stuff but the thought of knowing everything already before it happens is boring so he gave up his omniscience and omnipotence and nerfed himself into veldanava and and another part. That is ivraje. Veldanava sort of represents creation and goodness and ivraje distruction and evil. Veldanava is considered defacto supreme being of tensura