When a person awakened its mana and became an awakener they gained the access to use mana.
However the way they will use mana was decided from the moment of their birth and their awakening.
Though mana was situated everywhere in nature but for an awakener it was mainly situated densely in their heart.
As one's rank increased, the awakener slowly started forming rings over their heart, which in return helped them gain more mana and made it easier to accumulate mana throughout their body.
This was the first condition for reaching superhuman level.
The formation of rings usually takes place once the awakener steps on the superhuman level or in the system's language S-rank.
After which formation of nine rings takes place which were the maximum of rings that anyone had ever achieved and was also the limit.
Usually as the mana spreads throughout the body, upon doing exercise it breaks the limiters of the body.
But those with weak cores took a lot of time to get their mana spread throughout the body, thus their rank increased slowly as they went upward in ranks.
Due to the mana being densely situated in the heart a normal awakener of low rank wasn't able to achieve body reinforcement and mana coating.
However, after years of battle and research of sword god during the 'war of cataclysm' he found out a different and more efficient place to store mana for weapon users.
This method was exponentially great and was very beneficial so much so as it helped the weapon master to achieve a second stage of mana coating, named as Aura.
The method that sword god developed was of forming dual cores, one in heart and other in dantian.
He created a path through his breathing technique where his mana was stored in two different places simultaneously.
The core in the heart adds rings and the dantian core makes it stable and once the core in heart reaches its limits, the dantian core carries other rings and the core in heart makes it stable.
this was the way how sword god was the first to reach 9 rings and in systems term SSS+ rank.
Later, due to the death of the sword god at the end of the war, the son of sword god and the patriarch of their family at that time decided to keep some part of it a secret and made it a thing to be passed down in family generation by generation.
***
Kalki's talent was already the lowest of low that you can expect due to forced awakening, so moving through the conventional path to gather strength was never an option for him.
Thus, he had long decided to use everything he could to increase his strength even if it meant using methods by devil followers to gain strength.
Instead of taking the hard route, at one time he thought of getting 'Lutik elixir' but later decided not to as it would have caused too much of a butterfly effect in too early of the story.
Kalki forced his mana that was moving towards the stomach where the essence was to move towards the largest mana meridian of the body situated in the solar plexus, named as dantian.
It was not easy to do so, after all forcing mana to move away from the essence felt like a tug of war, but with 'percievoid' skill in play it was a little easier.
Even though Kalki's eyes were closed, the world was very much clear to him.
He observed his mana core in the heart and remembered the monster core that he saw earlier. Although now crystallized but when monster was alive it behaved a little similar to what humans core did but at much more efficient level.
Usually it wasn't possible normally to see mana core of anyone nor it was possible to analyze it. Because no one every has a necessity to form a core before, it never piqued anyone's interest to analyze mana cores and form dual ones which was a risk to take at a whole other level.
As magician usually has way more connectivity with mana and a whole rank high in mana stat it was not possible and beneficial for them to form dual cores. Thus, they never cared for it.
Forming it will only led to increase in difficulty in managing mana for them or cause mana bursts in meridian due to unnecessary high mana in body.
On the other hand the weapon masters usually has low mana and less connectivity with it, in beginning this was a disadvantageous for them and also was the reason which made it impossible for them to weave mana during formation of mana core.
However after the founding of Aura and 'aura dantian' which was a washed up version of what sword god's son revealed to the public, the weapon master's were finally able to step up and compete with magicians neck to neck.
With immense focus Kalki structured the dantian core similar to what it was in his heart, however it was not exactly the same.
From the observation that Kalki did, there were basically two major differences in the mana core of humans and in the mana core of monsters.
First one was the crystallization of the monster's mana core, which gave them many benefits but wasn't beneficial for humans at all.
Secondly the mana core of humans only had two chambers, one where collection takes place and other where purification happens, before distributing mana to the whole body. But in the bodies of monsters 4 chambers were present.
The first two worked similarly to how it works for humans however the other two had different functions, one act as the gathering point for the bloodline ability's mana pathway and the last one act as the mana storage for emergency purposes.
The emergency purpose mana was the reason behind the monsters going berserk and using very powerful skills just before their death.
Kalki also tried to replicate the monster core during the formation of the dantian core.
If Kalki was trying to build it the normal way then it would have never been possible for him to achieve it. However his mana art skill works wonders.
Only due to his mana art skill he was able to see the working of the monster core closely while he is alive in the microscopic level detailing. On top of that it also helped him to control mana more clearly while building his core.
As Kalki completed his mana core formation he closed his mana art skill. And due to the repercussions of his skill he lost his consciousness that he was holding on to.