A homunculus (the Arcane, or Draconic, Language word for "Little Human", plural form is "homunculi") is an Alchemical construct of sorts that mimics a humanoid creature, most commonly a member of one of the races of the Blessed Living. This is not the only possibility however, as homunculi have been created in the form of Goblins, Orcs and other races as well.
While it is not generally known how homunculi are created, it is widely believed by more experienced Alchemists that homunculi are a product of High Alchemy. Unlike other Alchemical constructs such as Golems, homunculi have the peculiar trait of Free Will, and are able to act and move about of their own volition. This is usually restricted, however, by the peculiar and seemingly unbreakable loyalty they have for their creator or creators. Homunculi of nearly every race have been created, though none have been created that bear the likeness of Nephel or of Eidolon for reasons that scholars can only guess.
All homunculi bear the the icon of the oroboros somewhere on their body, a sort of unexplained after effect of the creation process. In addition, what little information does exist would suggest that homunculi have Alchemical weaknesses that will result in the basic components which construct them breaking down more rapidly. This equates roughly to a weakness to certain substances such as silver, poison, or acid.