Pulled out of another thread (I think it's worth its own discussion, and didn't want to side-track the other thread):
The Black Council is I think largely Cowl, and his allies, agents and cats paws.
I think this highly-possible.
It's
at least as likely as a large "Black Council" (comprised of 5-15 wizards & other entities) all working in the shadows with nearly-perfect security.
Three may keep a secret, if two of them are dead.
-- Benjamin FranklinMab doesn't know... really? The supernatural-world's master-manipulator, the one who scared most of the Spookyside into signing her Accords?
Anduriel doesn't know... really? The
Master of Shadows was caught by surprise by the info Harry dropped on him in the Shedd?
We all think there's a whole
group of practitioners out there who are keeping
everyone(*) ignorant of their little glee-club...?
...
Really?
I think a single BigBad -- let's go with Cowl for the nonce -- is more-likely the entirety of the "senior council" of the "black council." He'd have his fingers in a bunch of pies, and likely presents himself as an "equal partner" to everyone else who's sharing a given crust... but doesn't see it that way. He's the baker, they're just the pies.
Papa Raith & Duchess Ariana & Margaret LeFay and "the Starbabe plan" was one such "Black Council" pie (they tried & failed to recruit Ebenezer).
I suspect there was another "Black Council" with Kemmler on it; that may have been a "Council" of two (though I suspect Blampire involvement, particularly Mavra).
There is another "Black Council," wielding Hellfire, who was involved in the assault on Arctis Tor. Harry pinned that on Thorned Namshiel, but I am unconvinced; maybe Nammy, but maybe someone else. Harry named Nammy to Mab (but she didn't explicitly confirm Harry as correct).
Some of the early Casefiles (Sells & Kravos getting their outsized magic; enchanting the Hexenwulf belts; etc) could have been solo op's, without needing any "Black Council" partners at all (likely just a cut-out man as a "junior partner" to deliver the goods to his dupes: a Glau, a Madrigal, etc).
The Outsiders & Nemesis are also involved, of course. Whether Cowl himself is Nemfected I'm unclear; Cowl may just be trying to use the Outsiders to his own ends.
Or, just maybe, Cowl himself is merely the cats-paw of an even-bigger BigBad. In particular, Cowl dancing to Nemesis' subtle music seems not-unlikely-at-all; he doesn't have to be Nemfected to get manipulated by an undetectable supernatural agent...
(*) Possibly everyone but Odin? Vadderung tells Harry something to the effect of, "It's all connected, and you are just now beginning to see the connections." Presumably, then, Vadderung has spotted those connections and figured out their common origin...