Familiar

In European folklore of the medieval and early modern periods, familiars (sometimes referred to as familiar spirits) were believed to be supernatural entities that would assist witches and cunning folk in their practice of magic. According to records of the time, those alleging to have had contact with familiar spirits reported that they could manifest as numerous forms, usually as an animal, but sometimes as a human or humanoid figure, and were described as “clearly defined, three-dimensional… forms, vivid with colour and animated with movement and sound”, as opposed to descriptions of ghosts with their “smoky, undefined form[s]”. (Wikipedia)