Seven Types of D&D Familiar

Ever since my Illusionist first cast Find Familiar in the dim and distant days of AD&D, I have been obsessed with magical companions, however, they're one of the most under developed areas of spell caster role playing and so today I thought I'd turn this blog over to looking at familiars and thinking a little bit out of the box when it comes not only to designing them, but to creating game mechanics around them.
Familiar was a term first used in the 17th Century when people accused of witchcraft described Satan's imps and how they influenced human affairs (the entire concept is probably the result of torture, it must be acknowledged), and they were detailed in Witchfinder General Matthew Hopkins book, The Discovery of Witches:

The small black cat Pyewackett has had probably the best career out of Satan's original line up here, appearing in all manner of YA novels, though Vinegar Tom is planning a comeback and has a new agent.