Song Cheng didn't know where his elder sister-in-law had gotten the idea that "Reappear Calamity required resistance," but based on his observations, her idea was likely incorrect because there was no such thing as resistance.
As for the principle of how the soul became stronger, he had also roughly guessed it.
If a Soul Refiner could become stronger by consuming "Soul Strengthening" type pills, then... for a Noble Family Child with an Innate Ghostly Soul, in reality, "Ghostly Soul" was both the starting point and the endpoint.
To break through, one had to rely on the power of evil spirits.
To rely on the power of evil spirits, one naturally needed to comprehend and accept Reappear.
This was very similar to the "transcending tribulation" often found in the cultivation novels Song Cheng read before his transmigration.
Heavenly lightning was a tribulation, yet it could forge the body.
Reappear was a tribulation, yet it could strengthen the soul.
One and the same principle.
