After making sure everyone had their training plans, Karna decided that it was time for him to start his own work.
He had already prepared the plans for improvements in his magic for his final battle with Acnalogia and now Ankhseram. He had started preparing the plans when he had acquired the demon slayer element when he took out Lullaby. Plus, later learning about Nirvana from Devil Island had also added to the improvements of this plan.
The system options talking about a power similar to the Shadow Monarch was the final nail in the coffin when he finally got an idea about what his endgame form was going to be. That was why he told the system he was choosing all the three options it had shown him that day.
A physical strength of a dragon brawler was needed for his body to be strong enough for the rituals he was about to put it through. Control over the power of death, equivalent to that of a necromancer, was needed for focusing the energy to make sure it did not rampage and kill him during the procedure, and finally, the path of the warlock was needed for his body to be compatible to handle the stress of what he was about to do.
He opened up the system that had created a complete blueprint.
A blueprint of a black heart similar to that of the Shadow Monarch. Karna had designed it, seeing that the usage of death energy was harmful to his body the first time.
Even though his body had adapted to the usage of death, it still got damaged each time he successfully broke through a new sealing of his death demon slayer magic.
So he was going to create a reactor that would supply him with magic every time he used the death slayer energy. For creating it, the only thing missing was the blueprint for creating a devil's heart.
And Karna got that from Hades, who had created the original infinite magic reactor, the Lumen Histoire.
Hades had created it thinking that he could rid Mavis of the curse if he overloaded her body with another form of magic. But the curse was woven into her body too deeply, so he was unsuccessful and had created a weapon capable of destroying the whole world.
Later on, he had created another version of the magic reactor, the devil's heart. But unlike Lumen Histoire, this one did not have infinite energy, but its magic generation was high enough that the user's output never surpassed its recovery.
The difference between the two was the base material used in its creation. Mavis's body had complete resistance to death and was essentially immortal. Thereby, the reactor created using that body was able to produce an infinite amount of magic that was never-ending.
Though Karna wouldn't be able to create an infinite reactor, a normal devil heart's output was more than enough for him to fight evenly against foes in future battles.
He looked at the blueprint of the devil's heart based on his death energy, and then he went to the next blueprint. A similar design, but unlike the first one, which seemed to facilitate the element of death, this heart's design seemed to be emulating a conceptual life, which was the complete opposite of the death energy.
[Calculations from the rituals of Nirvana are completed. The spell can only be used on the host's body once, so calculations are being made so that there are no mistakes when the ritual is done.]
Karna read the system reply calmly, as it was all part of the plan he had made before.
He knew he was out of his league if he faced Ankhseram in a battle using the same death element. Unlike him, Ankhseram had experience in using the element for centuries, so expecting to defeat him using death energy was idiotic.
So he decided to use the inverting power of Nirvana to get the opposite power of death to battle Ankhseram in the future.
"It's a long shot, but having this power would give me an edge in the battle, and if not, it's still better to have it than not," Karna thought as he looked over the plans.
"Man, I will get an extra heart compared to Doctor Who," Karna thought with a smile, but suddenly his brows furrowed as he remembered something that happened during his battle with Hades.
"System, what the hell happened with my magic back on Grimoire Heart's ship? I saw something about an Apotheosis or something, and then there was some garbled language?" Karna asked, a bit confused.
[Apotheosis was representing the host breaking through a major wall in the path of controlling death. Right now, the host is just a level below Ankhseram when the control of the domain of death is taken into account.
The garbled text was the next form. Ankhseram is the closest to obtaining that level. And the system has no information whatsoever about what to expect when the host achieves it.]
"Wait, you are telling me I was going to achieve it if I had not stopped what was happening then?" Karna asked, his eyes widening at the realization. "How the hell does that happen?"
[Truthfully, host, I have no idea.]
"What do you mean you have no idea?" Karna asked, a bit exasperated.
[Host, I am made from the memories of the world destroyed by Acnalogia. I have never seen anything like this in the last world, so I have nothing to go on here.]
"That's a bit worrying," Karna muttered to himself. Knowing that he was about to easily achieve something that a literal god of death had tried to achieve by murdering thousands for hundreds of years was making him a bit worried about what was happening to him.
"Well, I can look into it later," Karna decided as he opened the system inventory and dropped the thousands of tonnes of ethernano crystals stored inside it.
"I will just do what I can right now."
A/N - hope you like it.