In the Strix Anthology short "There Are No Owls in Seattle", there's the following passage:
There’s Mackayla and her remarkable affinity for bolt cutters, of course, but there’s other ways, too. Ways they don’t know about. I’ve got the questions. Not exactly a usual trick of my bloodline—crushing minds and ruling beasts, sure, but a good bastard always picks up a few unexpected tricks, so while they’re smiling those empty smiles at me, I reach down into the guts of my soul and poke the Beast with a sharp stick. It snarls and rattles the cage, but when I ask it, it answers.
Question: Who here can give me what I want?
The hidden one.
Interesting. And who in this room is the most afraid, hmm?
The fat priest.
Well, no shit Sherlock, he’s sucking fire into his lungs for giggles. Last question: What can hurt me the most right now?
What. The. Fuck? No, that can’t be right. There are no owls in Seattle. I’ve made damn sure of that. Sunk myself deep into debt with some particularly nasty fuckers to guarantee it. So let’s try again. What can hurt me the most right now?
In this it seems like the Beast is a completely separate entity, and yet not. It seems to enforce the theory (much like Anne Rice novels) that Vampires are the result of some blood, shadow, and smoke spirit (a Beast? ancestor that is, or is a common ancestor, to the Strix).
I always assumed that the Beast is a sort of animalistic instinct, fight or flight and feed, just more overpowering than that.
Does the beast actually have a mind of its own? Is it, as an analogy, like a merged parasitic spirit that has continued your existence in exchange for feeding it's bans, whilst giving you its banes (kind of like a Geist, but you're dead)?