So, there's a thing I've been wondering, and I'm hoping someone out there has some obscure knowledge on the topic (or, should I be really lucky, one of the people who have knowledge we players don't!) could answer something regarding it.
From what's been shown, 'quickening', is a type of magick that can grant animals higher intelligence so that they can be of use to their creators. The ones we've seen include Poroggos (toads) and Skatene (Owls), and it can be assumed that Caith Sith is the same, albeit of Mhachi origin.
But I'm wondering, could this magick be used on any animal, or is there some kind of limiting factor that only makes it usable on certain animals? Could you, in theory, create a highly intelligent bear, or a squirrel, a coblyn, or even a Yol familiar?