Familiars are relatively independent magical entities whose visible form often resembles an animal. They are created by mages adept in conjuration magic and can be thought as living spells, except that they don’t really live. Familiars are not unlike machines, for they only follow the logic defined at the time of their creation.
Familiars are often short-lived and created for a specific purpose, such as scouting, gathering or transportation. They use magical energy for their functions and will vanish after using up the whole reserve. Although it is possible to replenish the magical energy of familiars, the simplest and most common method is to give them just enough energy to perform their task and let them vanish afterwards.
Although familiars usually take an ethereal form, combining advanced conjuration magic and engineering will allow them to be placed inside physical bodies. Familiars inside mechanical bodies are referred as golems and they are found tirelessly guarding important locations or performing tasks too dangerous for humans. Mining companies usually employ a large number of conjurers and engineers who make and maintain golems to do all the hard work.
It is also possible to place a familiar inside a dead body of an animal or a human. This practise has not seen much daylight, though, because using formerly living bodies is both inefficient and difficult. Needless to say, the general opinion and the law are also strongly against it.