Core Formation is referred to most as the most important realm in the entire Mortal Transformation stage and this is actually something I agree with for a change.
In Core Formation, it would be the complete evolution of the dantian. As one progressed further in the realm, the quality of the dantian would grow higher and higher. This would help increase the quality of the dantian making it able to evolve into a revolving core.
A revolving core is an evolution of the dantian and it would make absorption speed increase to unforeseen levels, but what made everyone so focused on perfecting Core Formation as much as possible was the variants one could receive. A variant was specific revolving cores or dantians that were based on the cultivator, the creation of one could be based on many things, personality, arcana type, cultivation technique, etc, it didn't really specify on one specific thing.
The problem was creating a variant was unbelievably rare and the only known way to do so was to build your foundation to the very limit till your dantian becomes a revolving core and that core evolves into a variant of one. It was a whole lot easier said than done, it was to the point where if I hadn't chosen an abyssal bloodline as my wish I was sure that I wouldn't form a variant revolving core, even if I was a Fallen. There were various types of revolving cores recorded in the Federation, there was the Black Hole Revolving Core, which gave a person obscene absorption speed and ranges it also gave a person a trace of the devouring abilities of a black hole could as well. This could give one a massive boost in cultivation speed without their foundation being weakened, based on these few advantages it should be among the top-ranked and one of the most desired variants, but isn't.
This is due to the Black Hole Revolving Core being the most basic and common variant of them all, if a supergenius even was able to become of the one percentile and condense a variant core there was a ninety percent chance at least that it would be a Black Hole Revolving Core. There were others like a Devil Revolving Core, Astral Revolving Core, Immortal Blood Revolving Core, etc, the possibilities were practically limitless. This was the reason why young geniuses paid extreme attention to this realm, they would suppress their breakthrough when they were at the peak of Arcana Condensation to build their foundation to the absolute peak since there was a chance that they would condense a variant Revolving Core as soon as the breakthrough.
Rizen is at the early stages of the nascent soul and he was able to hide his presence from me using the Dao of Darkness, this means that his comprehension of the Dao of Darkness must be near the sixth to the seventh layer of dao comprehension, his revolving core is the Shadow Firmament Revolving Core, this gives him an extreme boost in the shadow components of darkness, making him extremely efficient and extremely attuned to the stealth and hidden parts of darkness.
I started refining the Yin Arcana in my body and it began to turn into pure abyssal arcana that was being saturated to the extreme in my dantian. My dantian which color was translucent and was starting to disintegrate and wither away, this was a key part of the breakthrough as the energy would either reform a sturdier dantian which was known as the core of it would produce a variant of it. If one were to mess up the backlash would be extreme as they would have pretty much destroyed the dantian, making one a cripple immediately. There were medicines that we're able to restore the dantian in the event of it being destroyed but the civilization had to have the material and the power to create them and the weakest of them was a tier seven when Genesis was a mere tier five.
The scarlet-black energy began to reform the dantian and a searing heat was spreading throughout my body. Unlike the heat before this one burned. Sweat and steam were pouring out of my body to the point where my entire body and even my room were covered in a fog.
After what seemed to be an eternity the heat finally faded and I released a turbid breath of Arcana, I was shocked to find out that I actually broke through to the peak of the third stage of Core Formation. For average people 1/3 of their dantian would've completed their evolution in the cases of people who gained variants they would've completed 1/3 of the creation of their variant.
I looked into my body and found that in the place of my dantian was a scarlet-black flame as it seemed to be smelting my dantian, but there was something else in it as well.