For ghosts to enter the Empyrean Stage, Davis learned from Yin Li that they needed all seven physical souls.
How they would reproduce these lacking physical souls is beyond him, but he guessed that they should have the necessary resources in their sect grounds or at least know the whereabouts to aid their disciples in remembering the time they had been living, so that they could hunt their next incarnation.
However, what about the stage above it?
The Godskull was similar to the manifestation of a Truesoul. Without the Truesoul, how could they even think of entering the realm of divinity?
He was even doubtful whether the ghosts even contained the three spiritual souls in the first place.
However, what was clear was that Lady Thunderwraith not only knew about Godskull, but she also knew of the existence of the second level. Moreover, she also displayed signs of knowing about what the three spiritual souls signified.
