There are multiple advantages in crafting a new body out of fairy puppets. The most important one is it’s perfect compatibility with this world, but that was a given. The reason I prefer the fairies over any other wandering animal, apart from my distaste to killing, is that not only have they been refined and prepared by their previous master, they are also innately talented in magic.

I could find very little information on magic by mind reading because their powers are instinctual and require no understanding to work. I hope to be able to use this power as a crutch to aid me in understanding this world's supernatural energy, as well as a weapon to keep me safe.

Gaining access to those magic powers would be very easy if I were to possess their body, but we have already established this is not possible. Instead, I have to devise something similar to a weapon that retains the intrinsic qualities of a living being.

The closest example I can find in your memories is a high-tech organic mech. I would be the pilot safely confined inside the cockpit, only interacting with the world by using the robot’s controls. I would be perfectly quarantined and would have no more worries about distorting anything around me unintentionally.

The problem is that such a robot would be incapable of using magic and would be defenseless against simple magics like telekinesis. To defend against or perform magic, I need a much deeper connection to the entire body. I would become more akin to a parasite, implanted so deep in his host as to become indistinguishable. Clearly, such a profound relationship would result in the body becoming contaminated, which would bring us back to square one.

I plan to make use of both methods. I will be detached from most of the body, but I will fully take over the nervous system, providing me with a network of rootlike tendrils that will give me indirect access to the rest of the body. The nervous system would no doubt pollute nearby cells, but I will absorb and regrow the tainted components. This means I will have to regularly intake small quantities of replacement materials to heal, but consuming physical food as a substitute to pure energy seems to be the norm for the local ecosystem anyways.

Having worked on the physique of an indigenous species and having examined the way it reacts to the demonic corruption for days, I have already designed my new body. I have decided I will outwardly resemble the giants, as they appear to be the most civilized species I have come across so far.

Finding a quiet spot where I will not be disturbed, I excavated a large cave and began forging my treasure. I need to merge all the fairies together to make up for their petite size, amplify their magic talent and make space for some custom modifications.

I would usually use them as mere materials and forcefully reshape them according to my will, but the lifeforms of this world are billions of times more complicated than what I am accustomed to, and once again my lack of power is forcing me to achieve my goals in roundabout ways by systematically handling every little detail. With my current power I can manipulate individual cells, but I can sense that cells are not the smallest unit but rather they are themselves composed of a multitude of tiny particles I have no way of understanding. This means I cannot build or modify a cell and must make do with those I already have.

The first thing I need to do is disassemble the fairies. I generate hundreds of small force fields which I then fill up with all the different types of cells contained in the subject’s body. I end up surrounded by a multitude of different materials, most of which are transparent, but some, like the blood cells, have a deep and vibrant color. I digress, but the truth is that I have no idea of how this all works, and can only reconstruct the same patterns I saw within the fairies with the same cells, only the end result will be bigger since I am using more of them.

I ended up proceeding layer by layer, beginning with building the skeleton, followed by the nerves, the blood, the fat, the muscles, the skin… It made it very convenient to contaminate only the nerves but made it very hard to keep all the cells alive as they spent hours simply floating around in the air. I had to manually feed them energy to keep them vitalized, which was very tedious and forced me to rush through the project before I ran out of energy.

All in all, this method of meticulously assembling individual parts into a masterpiece worked great but is quite dull, as it holds no surprises. The lack of time caused the task to be more challenging, but that was more frustrating than interesting.

The surprise came after the operation was finished. Demons have a very high vitality, and as such, while an attempt at merging two demons together might fail, there is hardly any risk to their life. I had previously observed that the fairies were much weaker life-forms, but I was not prepared for the tiny incompatibilities in between cells to prove almost fatal for them.

As I withdrew my magical support from my finalized creation, I was horrified to see it start breaking down, as various parts of the body clashed. Each fairy was subtly different from the others, but I had deemed these dissimilarities insignificant, not expecting them to react so violently to one another. Once again, I lack the expertise required to solve the problem, and can only resort to continuously healing my future body, waiting for all the cells to adapt to their new reality.

The cells battled each other and got damaged, after which I would heal them, using this opportunity to discard any conflicting part of the cells. Another long and tedious process, as I had to individually heal each of the trillions of cells this body is composed of multiple times. This incident also greatly increased my curiosity about the microscopic reality of this world. Finally, after a few days of constant healing, the body stabilized and my first feat of power in this world was accomplished.