oh boy oh boy I'm so glad you asked!

Much like traditional homunculi, they're artificial humanoids created by someone called The Alchemist (mine are like 1 part golem, 1 part clone, 2 parts magic, and 3 parts crime against genetics). The gems in their chests are the "seed" they were grown from, and function as their heart, their source of magic, and their life force all in one.

While they are alive, and their bodies are made of fleshy bits with blood and organs and everything else, they're still constructs/dolls/weird little guys. They more or less fit a human template anatomically, but there are some notable differences in that they have no navel, nipples, or reproductive organs (and imperfect homunculi have no external genitalia at all) but they still have typical secondary sex characteristics.

Homunculi come in two different flavors: IMPERFECT and PERFECT. The distinction is, simply, a "perfect" homunculus is one that passes for human (at a glance) without any... abnormalities, and an "imperfect" homunculus does not. Imperfect homunculi are a lot easier and less time-consuming to make, but have a number of animal-like features that can range from "horned humanoid" to "what the fuck is that creature?"

Regardless of which category they fall into, all homunculi have brightly colored pupils and luminous eyes, and are aligned to one of four elements (fire, wind, water, earth). Perfect homunculi generally have more neutral iris/pupil combinations and subtly iridescent hair, while Imperfect ones have chaotic eyes with multicolored irises and have an all-over soap bubble/chromatic aberration look to them under direct light.

What's their purpose? hmm, who knows 👀💦 but they are my favorite little creatures, hehe.