Samuel was very very excited, much more than he had been in a very long time. 

The reason was currently sleeping soundly back at the hut while he whisked away into the grand library of the sect.

His experience with the demonic was non-existent, another gap in his knowledge, something he was only happy to fill. And while his disciple rested from their experiment he had come to the library to do a bit of study  

Having a demonic disciple would create certain complications the least of which, having to separate Elizabeth and Eishath. While he was at no risk, he could not say the same about his essence-refining disciple. So a part of his brain was already churning out a way to make that work.

Another was hard at work in creating the perfect speech to all Eishath to be accepted as a particular disciple. Sure, the demon may have tricked him under the guise of being a unicorn and he already devised punishments he would enact to remedy that infraction.

But at the end of the day, she too was a cultivator on her path, and he had once vowed to be the best master to his disciples, them being a demon did not change that vow. The others, however, may not see it as such, and as a result, he needed to convince the grand elders, otherwise.

Something he would do the moment the tournament ended. Thankfully, he had taken the time to read about how disciples could come under a master, and in that giant wall of text, there was a section on special case disciples and ways to appeal to the grand elders to teach them. He was sure Eishath qualified.

A curious way in which Samuel's brain worked was that he was not built to understand or appreciate social nuances. A demon was looked at as universally evil and as such there was no way the grand elders would agree, if anything, it would hurt his position quite a bit to argue for her.

Even Elizabeth and her sheltered upbringing would understand that what Samuel was doing was a misguided idea at best.

Samuel's single-minded thoughts brought him back to another obscure part of the library. Even more secluded than the ones he was usually privy to. Here there was book after book, scroll after scroll on everything demonic.

As with every other section he ever visited, he took the book closest to his reach and started memorizing it on the spot. When a single glance was enough to memorize an entire page, the action was made easy. 

What was not easy, however, was to accept just how powerful demons were. Especially, incubi and succubi(which he was sure was the variant of his disciple).

He was flabbergasted to find out that even the weakest of these monsters could not be detected without special equipment or the eyes of an enlightenment-level expert, which was quite frankly stupid. 

A being so weak he could kill with a breath had the power to evade his detection entirely was both fascinating and terrifying. The implications were staggering and it stroked Samuel's curiosity as much as the notion made him uneasy.

No wonder he could not detect anything with his soul sight, the demon had illusioned it to be entirely undetectable to an extent that was so real that reality itself accepted that to be a fact. His powers were still grounded in reality, outside of two exceptions one of which he still could not understand the depths of.

There was also the notion that succubi are fed life essence they have access to the core of that essence which was connected to the life span of that person and then fed on it. This was very well-known, in fact, he too had heard of succubi fucking people to death. Today he learned the reason why.

Eishath did have a unique constitution it simply happened to be a demonic one. One that had been sucking on his life, though that part he already noticed and outright ignored.

She only took a couple of hours per feeding and he had centuries to spare.

The more important fact was the change exhibited during the experiment they took in merely hours ago. This library gave him information on what might be happening.

An obscure piece of lore he came across was the fact that demons could change when exposed to enough high-density power.

But based on the information given, he needed to have expended hundreds of years at once to get that to work on an essence condensation rank succubus. Shouldn't that have made him lose a massive chunk of his lifespan?

*Samuel's unique mind had yet to figure out that his 'World Seed' was also an elixir of eternal life and he was already past the coveted eternal life stage of cultivation. Even Eishath figured out this little titbit about our main character... I made my mc a bit too unique... Whatever! I have this whole story to fix him!*