After the Divine had restored the upper planes, Pentharion began the next stage in his plan for ending the Dark Celest Era, in honoring the Treaty of Mechanus and the Infernal Pact, he declared the Primordial Pact illegal. Instead he declared a new balance upon the material realm, ordering that the primordials to be removed from power, and banished back to the elemental planes, and that the Material world would reflect the balance between all realms.
In the Declaration of Pentharion, He allowed the Divine to return to Prime plane, and work to banish the Primordials, and once the Primordials were removed, the Divine would once again remove their influence the material plane. By his decree none between the Divine, Elementals, Demons, or Devils shall own most of the material Plane, it should be kept in balance as best as possible. Only the primordials were banished from that level of existence for their power was considered too great for any to contend with, requiring the intervention of the Divine.