Self-consciousness can be a good thing, but not necessarily so.
For a Master of Miracles with poor aptitude, directly summoning a remnant soul with rich combat experience to fight can have significant advantages, since the original entity is already intimately familiar with its own power.
Conversely, if the Miracle Entity's understanding of a certain power surpasses that of the original entity, then personally controlling that power could be stronger than the source of the power itself.
Just like the Empress of the East; she personally took control of the Thunder Demon God to confront Baal, and she was able to fight on par with Baal, who had already refined his power to an extremely high degree.
It must be said, this is truly terrifying.
Keep in mind that Baal was once a formidable figure in the Primordial Era for the Gedemon civilization, waging wars in the south and north, known as a War God and Thunder Diety.
