Bring Me Victory

There is only one sole factor that determines what a Homunculus is. He, she, or it, must be an artificially created being. Therefore, simply being infused with a traditional Philosophers Stone will not turn someone into a Homunculus, as was the case with Van Hohenheim. In fact, it is not even a requirement that a Homunculus have a Philosophers Stone at their core, were someone to discover another way to sustain their lives. Nor is it necessary for them to possess any unique traits or abilities. A Homunculus is simply a living being that was created through artificial means, namely alchemy.

The Father has utilized various methods when creating a Homunculus, but each one has stemmed from the same base process. He first extracts a piece of his own soul; it is this element that allows the Homunculus to become an intelligent, living being. He then empowers this soul fragment with the countless souls of others, or more specifically he takes from the mass of Xerxian souls within himself. These souls have been reduced to raw energy, and pose no fight or threat when combined with the new Homunculus. This energy is what allows the Homunculus to regenerate, as as well to use their own unique powers and abilities.

Primarily, the Father determined what abilities the Homunculi received, and designed them specifically to complement one another. However, as he extracted an individual sin from himself with each soul fragment, there are some characteristics that manifested naturally by result of the raw sin existing at the core of their being. For example, the appearance of Envy's true form. Predominantly, though, the Father selected their traits and abilities. Both extracting a piece of his soul and granting powerful abilities to a Homunculus draws from his own energy, and therefore he must exercise limitations when doing so.