Altair was conducting a crude experiment. He had begun to dismantle the Sacred Gear given to him by Azazel. Through external experiments, he could discover a little about how it worked, but he could only get so far. To learn more, he had to destroy it, find a way to reverse engineer it.
Each part of the Sacred Gear was composed of spells, layered on top of each other. It was chaos, all bound together by the will of the being with whom Azazel had made the contract. Altair had been studying each spell. It wasn't particularly complicated, but there were hundreds of them.
It was tiring; he had been at it for days. Five days ago, he had moved entirely into the Marchosias mansion, although he would have to rename it soon. He had put it off; he needed something first.
Five days of analyzing the spells in the room.
It was supposed to be a replica, created based on an authentic Sacred Gear. Even so, it wasn't very easy, the most complex project Altair had ever encountered.
Finally, after so much work, he managed to reach the center of the artifact. He could feel a heartbeat inside, not that of a heart, but the magical pulsations typical of the soul.
As he took it apart, he could sense the soul within becoming increasingly unstable. After completely dismantling it, he felt the soul disappear, not dying, but escaping. He had felt Raynare's soul die when he killed her; he knew the feeling.
"Shit," he said when he discovered why so many spells were needed.
Each spell was designed to replicate tissues, and the tissues as a whole formed an organ. Or that was the crude explanation he could come up with.
A sacred gear was an organ, and it required veins to stay alive, although these were magical veins that maintained the power of the soul and provided quick access to it. It was a magnificent project.
"An organ, an organ," to design it, he had to base it on what an organ was. It was initially formed from cells, which then formed tissues, and these tissues ultimately formed organs. But organs are not isolated; everything in the body is connected. For that, he needed a circulatory system, one that linked it not to his body, but to his soul.
Azazel's sacred gear was made of spells, but Altair could do it with runes, as long as he could find a suitable sequence for it. He needed not only to create a circulatory system, but also one that could support and be compatible with the function of the sacred gear he wanted to create.
As for the body of the sacred gear, he had decided to use Marchosias's staff.
Altair and the late devil had reached an agreement. Altair would give him revenge, and Marchosias would agree to a contract to form a Sacred Gear, or the version Altair would create of it.
Marchosias was consumed by revenge; the Sitri had taken his life and destroyed his family, or so he interpreted it. Before dying, he had left a fragment of his soul in a gem inside the staff, something like a Horcrux. Altair would not be surprised if Herpo had some connection to the devils.
That fragment of his soul was in limbo. Altair agreed to bring infamy and humiliation to the Sitri family... although he didn't specify how. 'Cuckolding Lord Sitri will suffice, won't it?' Marchosias wanted to see the family destroyed, and Altair could, in a way, destroy its female members.
That was why they had reached an agreement—a vague one for both of them.
Altair promised humiliation. But he didn't specify how.
Marchosias promised strength by being part of the Sacred Gear, but he didn't say he would obey Altair. As far as the young man knew, the devil could seek to control his body. For that, he needed countermeasures.
The staff was made of Orichalcum, a metal incredibly conductive to magic. The metal would serve to create the cells and tissues in the "organ," while the runes, since it seemed more feasible than casting spells, would simulate the circulatory system of magic. The fragment of Marchosias' soul would serve as the core, of course.
Now, you couldn't just take an organ and put it inside the body. Well, technically, it is possible, but the person would die most of the time. The body can distinguish between what is its own and what is foreign, allowing it to attack all agents that should not be present in its body. They can recognize another person's organ as foreign and reject it.
That is why genetically compatible people, mainly siblings or parents, are used for transplants, and drugs are used to suppress the immune system.
Altair thought about how to solve that problem. Magic was not a physical thing as such, but it was still capable of detecting foreign magic and fighting it.
Of the unforgivable spells, this Imperio mixes the caster's magic with the victim's magic and consciousness, thus enabling it to give orders that will not seem strange while in a state of complete peace. It disguises itself to camouflage itself in the target's magic.
Altair suspected that Cruciatus worked similarly, but in reverse. The caster's magic combined with the target's magic, seeking to be as different as possible to create the most significant rejection, and it was that rejection that caused the intense pain.
Even the Killing Curse could be the same, going to a much greater extreme than Cruciatus, where the caster's magic overwhelmed the target's so much that the struggle, the rejection, ended up causing instant death.
Magic was strange, based on intention, and it was possible that in order for the intention to be fulfilled, the magic itself would take paths that the magician was not aware of, adapting to reality.
Be that as it may, he could create a spell to suppress his magic, but that would leave him vulnerable to possible possession by his next resident devil.
'To create the Sacred Gear... I need Marchosias' soul to act as the core, but I can imbue the 'tissue' with my magic.
Altair suddenly opened his eyes.
'Yes!' he wanted to shout.
Altair possessed a remarkable ability to absorb magic—hornfire dust.
Altair planned to reforge the orichalcum. Similar to how Damascus steel was created to form its patterns. He would fold it and then inscribe runes on it. That way, he could build the circulatory system more efficiently. He would fold it over itself hundreds of times until it had accumulated layer upon layer. Marchosias's soul was in the gem inside the staff; he could insert it later.
Between each fold, he would add Hornfire dust charged with his own magic, making it more compatible with his own body.
He wondered if he would need to create the circulatory system in the orichalcum, as it was already a fairly outstanding conductor. But the orichalcum at that time was a conductor; it could conduct magic from one end to the other, but the system would fuse it with his magic and soul.
Altair needed to investigate further. He still needed the spells to make the sacred gear intangible; Azazel's had been destroyed quite quickly, and he hadn't been able to study them in depth. He might be able to discover them better if he investigated another Sacred Gear.
"Too bad they don't fall from the sky."
Altair began to think of alternatives. He didn't know enough about soul magic to understand how to make the fusion between the sacred gear and his soul so perfect that the sacred gear would also become intangible.
He drummed his fingers on the white table he was working on.
"Can I connect the tangible with the intangible?" he wondered, although it was riskier.
Altair brought the magic to his hands, hardening them, and watched as they changed color to a pale purple, similar to a bruise. Magic could go into his body and alter it, so it wasn't a silly idea to assume it could be the other way around.
He weighed the idea of transforming the Sacred Gear into a physical organ that could connect with his magic. That way, he would save a step. But it would also create a weakness by making it physical, as it would also be exposed to attacks.
"Damn it," he said to himself as he covered his face with his hands. He had reached a point where he couldn't move forward due to his lack of information.
Altair stood up and, with a snap, appeared in an adjoining room.
Lily was wearing a white lab coat as she worked with blood samples, not only human blood, but also blood from the devil. Both samples belonged to her. Why did Lily have frozen samples of her own blood? Altair didn't care.
"Lily, I need information," he said, and the woman turned to look at him.
"About what?"
"Horcruxes... soul magic," he told the woman.
"I thought you were quite skilled in that area. You can sense souls," Lily said with a raised eyebrow.
"Sensing and understanding are not the same thing," he replied.
He had nowhere else to start but the Horcruxes.
And if there was one person who knew souls better than Lily Potter, Altair didn't know her.