The concept of "age" is meaningless for them, as they receive from nature all necessary knowledge and reasoning at the moment of birth. The maturing of their bodies into the adult stage does not take years like humans, nor do they grow any older from that point on. As an example, despite their mature appearance and personalities, Leysritt and Sella have lived for little more than two years.
A perfect homunculus is essentially a man-made artificial extension of nature that, external factors aside, will not die for as long the planet is healthy and has mana left. However, the price of being given life through such artificial means is that the homunculus will invariably have some sort of physical defect (small stature, short lifespan, lower intellect or lack of reproductive capabilities are just a few examples). Even with their potential longevity, they are below humans when it comes down to their strength as life-forms.
Despite having the same form and cognition as humans, homunculi are ultimately different beings due to their possessing a powerful Magic Circuit. Regardless of how fragile they are, their Magic Circuits makes it possible for the homunculus to achieve powers that are beyond an ordinary human's. Fundamentally different than the magi that are humans with Magic Circuits, homunculi are better defined as "Magic Circuits with a human form". Not "something made to be a magus", but rather "something made to be a Magic Circuit".
The homunculi created by the Einzbern, even those regarded as failures, have enough magical power to pose a threat to the Enforcers of the Association. Also, their knowledge of Magecraft comes from being branded with a standardized reverse-type magic crest. The models based on Justeaze, such as Irisviel and Illya, share the memories and personality of the original. In a way, they're the same being. Illya herself is a very special case and her very existence can be considered a miracle in itself. She was “birthed” through conventional means by her mother, Irisviel, although she was put through several magical treatments while still in the womb. Said treatments made her body become even more unlike that of a human being than other homunculi and are supposedly the reason why her growth halted in pre-pubescent stage and why of her very limited lifespan.
The homunculi of the Einzbern are created from the knowledge passed down by Justeaze Lizrich von Einzbern, known as the "Master of Northern Alchemy", and Kiritsugu Emiya claims that none can match her descendants in the process of creating artificial humans. Created through cultivation tanks, they are of a high quality.
Frankenstein's Monster was a homunculus made after the basis of the "ideal human." Although she wishes for a mate of the same kind as her, she sees herself as being fundamentally different from other homunculi.
Mephistopheles is a homunculus created by Georg Faust. Dr. Faust, with his gifted engineering, has advanced homunculus technology several generations ahead of his time, but due to his strange nature and sense of aesthetics, he strengthened the Homunculus' ego. A Homunculus that is exceedingly quite human———that is the key part of "Mephistopheles" 
Yggdmillennia creates homunculi using techniques stolen from the Einzberns and other great alchemical houses, but their level of expertise is menial compared to that of an expert. They consider that sufficient enough for creating soldiers, servants for their castle, and living magical energy batteries for Servants.
Those created as soldiers are built to be able to wield large halberds and use powerful magecraft, potent enough to easily match an average magus. Created as disposable soldiers meant to overwhelm in numbers, their lifespans amount to only two months due to being born with various defects.
However unlike other homunculi created by others all homunculi crafted by the Yggdmillennia are connected, however weakly, by pathways similar to that between Masters and Servants. One of the results of their mass production, possibly – as while they had a critical lack of individuality, they could all receive important information such as one another’s survival from anywhere without any need for conscious efforts such as telepathy. Of course, such data was not necessary to them precisely due to their sameness; the death of another homunculus was just one more number in the grand calculation.
Homunculus (ホムンクルス, Homunkurusu?) and Proto Homunculus (プロトホムンクルス, Puroto Homunkurusu?) appear as Assassin and Lancer class enemies in Fate/Grand Order. They drop Ascension Items such as Homunculus Baby (ホムンクルスベビー, Homunkurusu Bebī?).
- Einzbern Master
- Frankenstein's Monster
- Illyasviel von Einzbern
- Irisviel von Einzbern
- Justeaze Lizrich von Einzbern
- Rani VIII
- ↑ Heaven's Feel route - Day 16 - Gift
- ↑ Heaven's Feel - Return to the Spring
 Fate/Zero Season 1 Boxset - Drama CD 1
- ↑ Fate/Apocrypha - Volume 1
- ↑ "Fate Grand Order Material I"
- ↑ 6.0 6.1 Fate/Apocrypha volume 1
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