Julian's organization was called the True Underworld Council, and its original founder was the progenitor of the True Underworld.
At that time, the progenitor of the True Underworld was not yet the progenitor, and was competing with another nearly progenitor-level entity for the opportunity to ascend. He recruited a large number of Children of the Spirit Realm from the Spirit Realm Main World to come to this world. Subsequently, the True Underworld progenitor succeeded in ascending to progenitorhood, but the force did not dissolve; on the contrary, it grew ever stronger.
A large number of Children of the Spirit Realm descended to the Wizard World, retaining their memories through the authority of the True Underworld progenitor and dispersed across different worlds.
Many, including Julian, did not think that the progenitor of the True Underworld intended to conquer and subjugate the Wizard World, which was completely impossible even had he become a progenitor.
