Familiars

Familiars are companions to Wizards. Since those who work magic are often shunned, a Wizard’s familiar is frequently the only one he can truly call friendly. (And only friendly sometimes—a familiar can as easily be crotchety or sullen.) Familiars come in a wide variety of shapes and sizes, and can have a wide array of abilities upon which their masters can call in the service of research, defence, spellcasting, and more. There are three methods by which a Wizard may obtain a familiar. The first is by creating a creature from unliving materials and imbuing it with life by magical means. Such creatures are sometimes called homunculi, though they are also known by other names, and the traditional concept of a homunculus—a small, humanlike creature—does not describe by far the wide variety of created familiars that are possible.

The second method of obtaining a familiar is to bind a living creature to your company and service. Cats, birds, and rodents are typical bound familiars, but nearly any other living creature can be bound as a familiar. Finally, familiars can be summoned from the Realm of Chaos. Calling Daemon Imps—and even more powerful Daemonic creatures—to become familiars is dangerous business, and only the most depraved Dark Mages attempt to do so.

Source

 * Warhammer Fantasy RPG 2nd ED -- Realms of Sorcery pg. 183