"Oi, Iris, pass me that spanner over there."

"Here~" Iris handed over one of the spanners normally clipped to Lily's toolbelt. Lily accepted it gratefully and returned to poring over the metal arm she was constructing for herself to replace her left arm. Iris pouted a little.

"You know, I do have a number of these tools you use inside me. It would be so much easier if you'd just direct me and let me handle the mechanic work. Plus, I'm more familiar with the metal you're working on, so I'd probably be faster, too."

Lily laughed a little. They have had this conversation numerous times. Iris kept offering to help, but Lily kept refusing her. It wasn't so much that Lily did not trust Iris' capabilities, but Lily wanted the opportunity to work with this new metal she had been given the chance to find.

The arm she was currently constructing was made of the same untarnishable metal that made Iris' egg and and armor of the machine. According to Iris, it was hard, conductive, could withstand extreme temperatures and would never rust. When she was finished, she would have an arm which would, in theory, be able to conduct magic far more efficiently than her legs, and would last longer as well.

Lily didn't know how long it had been since Iris had woken up - probably quite some time. However, throughout it all, the metal girl had proven herself to be a loyal and capable companion, and above all, a friend. She had no memory of why she was sleeping in the machine, nor of what happened to her before she was repurposed as a battery for the machine. She did, however, have in-depth knowledge of the properties and purpose of each component of the machine, which Lily accepted with equal parts skepticism and amazement.

For one, it seemed that the strange invisible projectiles the machine fired from its arms were, indeed, bursts of compressed, pressurised air. Within the carapace of the machine, there was a cluster of hitherto-undiscovered special ore that could generate either a pulling or a pushing force, depending on magical input. In the time that the port opened, it suctioned in air, processed it, and fired it back out at speeds which Iris claimed to surpass the speed of sound. Lily did not know whether anything could, in fact, be faster than the speed of sound - rather, she had not known that sound had a speed. In any case. she knew from experience that it was fast.

The strange beam of light which claimed Lily's left hand was explained to be a blast of pure mana. This magic was powered by a magical core hidden within Iris' chest, unremovable without killing her. This core allowed her to constantly absorb energy from her surroundings - heat energy, light energy, sound energy, ambient residual magical energy - and converted it into magical energy, which powered the machine and its armaments. For now, with Iris no longer serving as a battery for the machine, the core was powering only her. That said, being an inorganic being, Iris was unable to shape magic on her own, without the aid of some form of auxiliary specialised device.

Perhaps the greatest insight Lily garnered from Iris was on the nature of magic. According to the metal girl, magic was an artificial construct. It was created by humans as a weapon, and implanted in them as fetuses. This created a magical core within the heart, which developed within the host as the host matured. When the host died, the core would dissipate and dissolve, leaving no trace. This magical core, once integrated, would be passed down to future generations, and allowed the host to manipulate magical energy, an artificial type of energy that could be shaped by the human mind.

Each human's core developed differently, with different mutations, which resulted in the existence of what Lily knew as <>. Each core shaped magical energy differently, possessing higher efficiency in some shaping processes than in others. However, only organics could freely shape the energy from the core. Machines, like Iris, needed some form of conduit to shape this energy. For instance, the machine's right arm contained a device specifically designed to compress and expel magical energy, and its knife was designed to compress and convert magical energy along its blade to form an extended edge.

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Unlike organic cores, which generated magical energy by feeding on its host's energy sources, mechanical cores like Iris' had a potentially infinite supply of energy, as it could draw in energy from its surroundings. Attempts at implanting this more powerful core into organics had been made, but were apparently unsuccessful. Simply put, Iris had access to a much larger pool of magical energy, but was unable to shape it to her will.

Considering that magic had always been considered a naturally-occurring phenomenon, the revelation of its artificial origin was a groundbreaking discovery. If it was, indeed, artificial, then it suggested the existence of an older civilisation, certainly more advanced than hers. It would also explain many of the unexplainable things that Lily had seen since arriving in this wasteland. The academic in her sang in excitement.

…But scratching her academic itch could wait. First, she had to fix her lack of an arm to scratch it with.

Putting together her arm this time was both easier and harder than crafting her legs. The presence of Iris as an assistant allowed her to leave the measurements to the girl, and focus on the mechanical work, while her continued practice on her legs allowed for her to go about her work with practiced efficiency and finesse.

On the other hand, she only had one working hand. She had experimented with using her feet to perform the repairs, using <> to manipulate her legs, but while she was able to grip and hold the tools, the crude shape of her feet meant she lacked the ability to make more precise, dexterous movements. As such, she used only her right hand, slowly and meticulously cutting and tightening and fusing and welding.

The new arm looked much more like a human appendage than her legs, primarily thanks to the smooth and flawless surface of the metal she was using. It ended in a small hand with slender fingers, modeled closely after her remaining hand. Numerous lines ran along the length of the arm, indicating the areas where the different plates of the arms intersected.

Aiming to maximise the options available, she had, with Iris' help and knowledge, constructed her arm to be able to open up and convert, similar to how the machine's arm had opened, storing a number of tools and methods of attack. She didn't have nearly enough innate magical power to incorporate the magical beam attack into her armament, but she did include multiple other devices.

Finally, she stepped back, examining her handiwork. Iris came up next to her and stood with her. As thanks for her help, Lily reached over and patted the shorter girl's head, causing her to open her mouth slightly in surprise.

She took a deep breath, then took hold of the finished artificial arm and held it to her left shoulder. Closing her eyes, she sent her tendrils in and spread throughout the construct, linking all the seperate components to her consciousness. Perhaps due to her body becoming acclimatised to artificial limbs, the assimilation completed surprisingly quickly.

Stretching her new gleaming hand, she wiggled her fingers a little and moved her hand through most of her ordinary motions. No issue. Then she put the arm through some unnatural twists and jerks which would have dislocated an organic arm. No issue. She opened and closed all the seperate compartments, testing that she could access all the extra features she had installed. No issue. While the length and build of the arm was identical to her organic one, the weight was off. While it felt the same to her, due to the assimilative effects of her magic, she knew intellectually that it would be heavier, even if it did not feel as such.

She signalled Iris to back away, then crouched down, and sprang forward, spiraling into a tornado kick.

…her landing was off. She lost balance, slipped and crashed to the ground, causing a worried Iris to dash forward and help her up. As she grabbed Iris' outstretched hand, she grumbled in annoyance. She had expected this outcome, but it was still frustrating. The difference in weight was affecting her balance. Thankfully, she had prepared a plan in anticipation of this, though it was somewhat extreme…