How can a creature literally born from magic be restricted in its magical range?

Question

Mana pathways are a pseudo-nervous system that spreads itself throughout the human body and are what qualifies a person to be a mage. Along the pathways are mana gates, specific points that connect the material world to the astral plane. These gates are activated by a mage's life force through spells, allowing one to convert life energy into magical energy. The number of gates a mage has is determined at birth, with an individual's power depending on the number of gates they have. The amount of gates that a human being can contain are restricted by the limitations of the human body. However, there is a way for a mage to increase their power through external means that allows them to gain access to a larger amount of mana gates with no added risk to themselves.

Within each male sperm cell is a microscopic organism known as animalcule, a complete preformed individual representing miniature versions of human beings. These preformed humans develop and enlarge into fully formed human beings through the process of conception and birth. Magecraft allows individuals to bypass this convoluted process to create life in order to create a perfect servant loyal to its creator, known as a homunculus. These homunculi are grown within a specially built cauldron designed to hold magic brews. This brew is filled with various ingredients, such as eye of newt, as well as other lay ingredients, such as cow intestines and the seed of the mage in question. The resulting "child" emerges from this concoction as a fully grown adult, bound to obey its master's commands. Although they are intelligent, homunculi lack free will and individuality, making them the perfect servant.

As they were born from magic, Homunculi are immortal and physically difficult to destroy. As such, they are lack the limitations of the human body. This allows them to contain as many mana gates as their master wills or can afford, allowing them to achieve levels of magical power that human beings are incapable of. These mana gates are created artificially, and inserted into the body of the homunculus in a similar way to an organ transplant in a human. However, while they are more powerful magically, there are limitations to that power. While human beings are varied in the kinds of spells they can use, homunculi are limited to one specific spell at a time. These mana gates are infused with the power of an individually spell before they are placed within the homunculus, and must be swapped in and out as needed. This design flaw is unintentional, as most mages agree that they are better served with their creation being as diverse as possible. This forces beings like homunculi into areas of specialization, limiting their uses and preventing mages from maximizing them to their full potential.

The more magical a creature is, the more restricted its range of magic. How can this be the case?

Answer 1

Mana gates in a homunculous are all aligned the same way.

Consider wind. If you expect high winds you will need to fortify your building to withstand wind from any direction. But if wind only comes from one direction you only need to withstand forces from that direction.

Human gates are randomly aligned and so human bodies must withstand variable forces. The randomness also means that for any given magic there will probably be at least one suitable gate.

Homunculi have all gates aligned the same way. This allows them to be internally braced to withstand the destructive forces which are also all aligned the same way. Homunculi actually do not have more total gates than humans, but because the gates are aligned at placement they augment each other and have much greater power. The homogeneity of the gates mean that only spells fitting that gate alignment can be used by an individual homonculous - one or two at most.

Some homunculi can manage additional magics that do not align with their gates, more or less brute forcing a square peg into a round hole. The power associated with the multiple gates means the job gets done, but the resulting ill-fitting magic will be coarse, or the result bleeds into other effects. It could be damaging to the entity.

Realigning the gates in a grown homunculous is arduous and risky to the point it might be easier to make a new one. But the gates do realign as a group and so if an individual homunculous is desirable for other reasons realignment and a new set of magics is possible.

Answer 2

Depends on the rules of magic and the construction/anatomy of the homunculus, but here's some ideas

Spells passing through the constructs may harm the magic sustaining it

Homunculi are magical constructs sustained and powered at least somewhat by magic. As such, they have different pathways and gates than human mages do naturally, as their pathways are being used to sustain movement and following orders etc facilitating the homunculi's functions.

Having a homunculus attempt to cast most spells will almost always disrupt the homunculus' own magic and destroy the construct when a vital pathway is overruled or overpowered by the spell. To get around this, Special gates and pathway are created and grafted in or onto the homunculi to manually guide the magic energies and produce the wanted effects.

These additions are set in stone so to say, giving the wielder the ability to cast only the spell "programmed" into the construct, as it guides all the magical energy required safely around the homunuli's self-sustaining magical pathways. To change the spell being cast requires changing the construction of these additional gates.

Casting spells as a Mage requires something Homunculi lack

Humans are not magical beings innately, but some of them have magical pathways including these gates that allow them to wield magic in different ways and to different extents.

It may solely be these pathways and the gates that control and harness the magic energies, or in the process of converting life force to magical energy, the will of the user somewhat shapes the spells.

Homunculi lack a quality (Free will, Spirit energy, thought) that a living caster has that is required shape the magic as needed on the fly, relying solely on strictly constructed gate/path arrangements to consistently produce the same wanted effect. The homunculi essential just flips the on switch rather than concentrating mental effort as a Mage might.

Answer 3

Like @Wilik said, the mana gates would have to all be in synchrony. However, instead of mana flowing like wind, what if mana vibrated at different frequencies? Then, the gates would have to align to let the certain frequency pass through. Also, the more powerful the spell, the higher the frequency. Thus limiting the Homunculi to less powerful spells and only one spell. Additionally, the mages would have to build the Homunculi to a specific frequency to give them magical abilities. For any range factors, just say every 10ish meters (or yards, depending on your unit of measurement) that (give or take) 10% of the energy diminishes. So a target 10m (or yds) away would take 2.594 units of magic. That same target at 30m/yd would take 17.449 units of magic. The formula to graph it would be y=1.1^x, or y= 1.1 to the Xth power, with x equaling distance.

Answer 4

Channeling capacity.

Essentially, how much magic you can store in your is not related to how well you can channel said msgic. Picture it as a gun with a magazine, a bigger magazine means you can shoot more before reloading, but doesn't mean you're instantly a better shooter. Your homunculi may have many more magical gates than your average human, but their minds are structured in a completely different way, one that, although making them ideal servants, severely limits their ability to properly channel their ample magic reserves properly through spells like a human can. At best, they could release it all in a devastating burst, but the finesse needed for proper spellcasting isn't at the top of their list of skill proficiencies.

Alternatively, take a page off my own creation: the [redacted] are a race of creatures born from experiments performed on sentient magic items, granting them the ability to channel their abundant magic into the creation of powerful bodies they could control. Said bodies have a rapid regeneration factor and ample magic reserves, allowing them to manifest a large amount of spell-like abilities. However, their anatomy is structured in such a way that, despite having ample magic resources, that magic is ingrained into their tissues, causing an interference that severely hinders their ability to cast spells. Aka they have intense magical power, but their anatomy itself disrupts magic channeling, making it extremely hard to channel said magical power into spells.