Fear Inducing
Primordial Yins all have a different feel to them. But, regardless of what they might be expressed like, they all followed the same set pattern. The first was talent, the second was cultivation, and a tentative third was length of time.
The more talented and higher cultivation a woman had, the stronger her Primordial Yin would be. There was also evidence that this also scaled with the older a woman became, but this had a caveat as well.
A Primordial Yin couldn't increase indefinitely in strength along with a woman's age. The prerequisite was that she remained in her prime and didn't decline.
To someone like Eska, her Primordial Yin had been on the decline for a long while. Such a truth was inevitable. After all, she had died. If this wasn't considered being past her prime, then nothing would be able to fit this mold.