The origins of the first homunculus are cloudy at best, and the fact that many cultures seemed to have created them at seemingly different periods of time doesn't quite help to pinpoint the primeval creation. What is known however, is that when the Grand Alchemist Circle started to collect and record alchemical recipes, the practice of creating homunculi servants began to become more common, and popularized to a certain extent.
One of the most ancient recorded practices of the mass production of Homunculi was in an ancient Valerian scroll that detailed some of the tactics used by Shinobi of the old continent in the bloody conflicts between their clans. Taken from the extract of Ancient Valerian History:
"What makes up the human body can be found in nature, without fail. By collecting all these elements and performing the proper alchemical formula, one is able to breathe life into a fully functioning human body. When this formula was discovered, the Shinobi Sage Leontia thought she had discovered how to create life, and with this, the highly prized philosopher's stone, the key to immortality. Unfortunately, she was wrong. The people she created, if they could even be called that, were little more than empty husks, they lacked free will, and so it was determined that they lacked a soul.
This find wasn't a waste however, as she discovered that she could implant part of her soul inside these husks, and fill them with knowledge, using them as soldiers, little more than objects who could discard their lives easily while following their master's commands.
Without will they lack the want to improve, the desire to become better, and with that, they are incapable of surpassing a human in anything. A homunculus has the ability to learn extremely fast, but is unable to fully master something like a human would, making them unreliable at best to perform the more delicate tasks.
The advantage that Sage Leontia found in these flesh dolls was their emptiness, in fact, after she discovered that she could alter their physiology even further by leaving a few ingredients out and adding others, Leontia started to make homunculi that could not feel pain, making it easier to sew them back together after a task. She also devised a method to link her soul with the Homunculus, and issue them commands without even having to speak. Her will became theirs, and everything she wanted, they blindly followed.
The technique for the soul link that Leontia created could be done in a few ways, either by creating a direct blood bond with the homunculus, or by creating a focusing stone, which held the homunculus' life essence, and anyone who held the stone could issue commands to them, as long as they had the stone in their possession. The blood bond was a more straightforward process, consisting of creating two matching runes, one on the homunculus, and the other on the master. The homunculus would the sap the life essence from their master, and with that, he would be able to share his master's consciousness. This would leave the master weakened, and as such, there would only be a certain amount of homunculi that a master could link himself to.
The other method was to create a focusing stone, made with the coagulated blood of both the master and the homunculus, coated with a hardening agent that kept the blood fused together. The interesting part of this second method is that it didn't quite offer the same level of control as the first one. The focusing stone (or stones for some more powerful homunculi), acted almost like an actual soul, giving the homunculus some semblance of thought, and even enabling it to act on his own to a certain extent. The servitude however didn't suffer from this, as anyone who held the focusing stone was able to issue commands to the homunculus through his voice, while touching the stone.
Sage Leontia quickly discovered the full extent of what she could do with this power, and trained her own body and mind accordingly to her purpose. Most documents concerning her always described her as a very sickly woman, always leaning on her walking cane, despite being in her late twenties. More detailed documents however, from the people of her clan, say that she was like this in public because she was bearing the burden of many soul bonds. Leontia was rumored to be able to link ten homunculi to her person, and without her bonds she was so resilient that her flesh alone was able to stop a sword blade. After discovering that vitality and life essence was of paramount importance to controlling homunculi, that was what all her training focused on.
In her studies she also details the risks of creating homunculi, and the hazards of a failed creation. Occasionally the creation process might go wrong, which is to be expected with all transmutations, but in this case the soulless abominations that can spawn from a failed result are often quite deadly to the alchemist attempting the formula. Part of Leontia's training, and of all her apprentices, was in fact dealing with the abominations. She used to stress the importance of knowing the exact value of a single homunculus, even if they were to be used as tools, the masters of the homunculi should always know the price of their creation.
Failed abominations are an important piece of information concerning the creation of homunculi, and something that all that attempt it should be aware. Successfully breathing life into a homunculus is a tremendous achievement, especially because the chances of failure are much greater than the chances of success. There are three possible results to a homunculus ritual. The first is the success, where the homunculus is successfully animated and functions properly. The second is when the homunculus is not animated properly, and does not survive its birth. The third is when the animation is successful, but its body and mind are deformed, birthing a horrible abomination to the world, one whose only will is to destroy and consume its creator.
Homunculi don't have anything in particular that differs them from humans, by adding in the appropriate ingredients and raising them in a specific method, one is able to shape their appearance to their will. A sure way to know however, is that a homunculus will forever carry a mark on their bodies, the alchemical symbol for the soul, that which binds them and gives them life. This mark generally appears on their chest, above their hearts, but in rare occasions may appear in different locations. If the mark is destroyed, the homunculus will die."