Desiderius wanted complete affirmation of the demise of the 9 Anchors so that in the future, the Ancestors of these Planes couldn't do what Noah was doing and reverse this process!
He had waited for many years.
He had planned and accounted for many things.
He knew that the True Emperor of an Age was granted a unique connection to Reality when they took the Throne as it was the Key to Reality!
But this was it.
A Key of a Plane of Existence.
Existences that momentarily has access and controlled their Planes were special, but the power they would be able to exert was not something Desiderius was worried about!
He was affirming the extent of this power now as when his visage erupted with Seas of NULLITY, the authority of Reality moved as it was ushered by the True Emperor of Quintessence.
A plane's authority was something undeniable when utilized to an extent, but it could not be called upon too many times.
