A homunculus is an artificial human. While homunculi are very rare and most people will have never met one, they are significant to the story of SCSMUSH and warrant special mention. One of the main characters of SCS, Lily, is a homunculus and other important characters are either homunculi or homunculus-adjacent. This help file explains what that means.
First, a brief refresher: one quirk of Rithera's metaphysics is magic, like every individual, generally has some sort of attunement with at least one element and one domain. The notion of an element without a domain, as discussed in "help cosmology" and "help chaos," is paradoxical: an element in its purest state would generally be entirely Purification aspected, not lacking a domain. But the notion of a domain without an element, like "raw" Creation or Destruction, does make sense, at least as an abstraction. That is the power of the gods, which humans lack the aether to emulate. And souls are a composite of aether that is entirely domain-aspected, which is what makes them immaterial.
This has implications for the construction of homunculi: while artificial bodies are manageable, artificial souls are beyond humans to create. Ancient civilizations used druidic elemental magic to coax elements into forming the shape of bodies. More modern magitech-researching scientists could, Frankenstein style, restore a corpse to a functional living body. Fallen stars, being rare materialized souls, also make an artificial body significantly more easily inhabitable and so are typically used in making a homunculus. While demanding a lot of expertise, these acts don't push the limits of magic. Moreover, as discussed in "help death," souls are naturally attracted to bodies capable of living. The trick is in getting a soul.
There are a few ways:
* The soul of the freshly dead could be coaxed into a new body.
* Souls who happen to be roaming in the vicinity could be attracted to the artificial body, resulting in a kind of synthesis or hybrid soul dwelling within.
* A fallen star could retain features of the soul that once formed it.
In all these cases, the process of possessing the artificial body does some sort of damage to the soul: most commonly, it loses memories, and sometimes, it can be struck by surges of contextless memory that induces confusion. Additionally, artificial bodies are of varying complexity and not all function as natural bodies do: homunculi do not necessarily need to eat or sleep.
However, the less an artificial body functions like a natural body, the more a homunculus requires aether in order to sustain itself. Magical "digestion," meaning breaking down materials into the sort of aether consumable by homunculi, is not easy. Outside of snorting powdered elementals, a homunculus who can't eat will need to be equipped with some means of deconstructing materials. Notoriously, at least some homunculi who are deprived of the aether needed for sustenance go berserk and rampage seeking it out.
The key limitation on making a homunculus is that no one has managed to construct an artificial soul from scratch. (This is important because there are characters who have tried and failed and, were it possible, they would have succeeded.) But this may be a technicality. Insofar as a homunculus may be awakened by drawing a bunch of ambient souls into them and letting the souls sort themselves out, there isn't much practical difference between that and a new soul.