A homunculus is traditionally a form of artificial life created by alchemy or magic. Vaguely human shaped, the homunculus serves as a companion, helper and possibly a surrogate child for its creator. Popularized in sixteenth-century alchemy and nineteenth-century, it has historically referred to the creation of a miniature, fully formed human. The concept has roots in preformationism as well as earlier folklore and alchemic traditions.
Despite the name, they are not necessarily small, some homunculi are described as man sized and how man-like they are varies from account to account. This may be a function of how the creature was made and/or the skill of its creator while some are recorded as being able to speak, but most are mute. Other common unnatural features include wings, beaks, claws and fur. In a fantasy setting they may be hard to distinguish from imps and may be mistaken for a familiar (or may be a common disguise for familiars). In some accounts the homonculus will bear a more or less grotesque resemblance to its creator.
Methods of creation vary but most seem to be enthusiastic about the use of human semen which would seem to re-inforce the "surrogate child" theme and blood. Other methods involve a mandrake, a herb deeply entwined with human fertility, and retorts packed with herbs and and/or animal parts and incubated in baths of sand or manure for a given time. Sometimes the creator frames the creature's body with metal wire and/or clay and sometimes not; a man-sized homunculus could even be cast onto a human skeleton. Of course, one could use the skeleton of a child or a monkey for a smaller creation. Perhaps the simplest method recorded involved injecting semen into a fresh hen's egg, sealing the hole with parchment and then burying it in dung until it hatched.
It is said that homunculus possibly possesses no soul but it may, however, share part of its creator's soul if that is what clones do under the laws of magic. This may make it more or less susceptible to magic. It is entirely normal for a homunculus' master to be able to conduct remote viewings through his creature's senses, for this may be an inherent ability or normal scrying magic with an improved focus. Harming the homunculus may or may not harm the creator, but it's likely that access to one will provide substantial sympathetic benefits to magical sending aimed its creator. Since it is likely to be made of a piece of him/her, it will probably provide a strong link under the magical law of contagion.