Choice

Outside of Cassius' expectation, Dyon's lip curled.

On the mortal plane, it was probably impossible for someone to tell that Dyon was using a primordial yin to maintain his form. However, this wasn't due to a lack of ability, but rather due to a lack of knowledge.

The mortal plane had fallen into such a sorry state and many of their legacies had been cut off. Though the culture of protecting pure blood daughters still persisted, many had already forgotten why this tradition existed and even those who knew why lost the means of utilizing this method, let alone detecting its use.

However, the immortal plane was different. Normal people couldn't tell, especially with Dyon's immortal sense factored in, but, those who shared the bloodline Dyon was using would be able to sense subtle differences they could deduce to the root cause.