If Nailisi were to be able to create a Purgatory of Shadows in the 12 Notes of First Purgatory, the rules that she would have eventually extracted would have been more powerful than what was mastered by Agares.
Nailisi did not bring the subject up anymore after throwing that shadow warrior into the collection of purgatories, instead turning her attention to fight the god creatures in earnest.
The god creatures were not weak; they were actually hard to kill. That was because the Lord of Glory would have required several days to arrive. Amassing an army in the millions was but a test assault.
