Rereading TC, and I came across the scene between Harry and Rashid while on the docks and Demon Reach. Rashid remarks on a number of events that have him wondering whether Harry is part of the Black Council/Nemfected. We know that Harry isn't. We also know that most, if not all, of Harry's cases involved him working against the Outsiders. One thing I have issues with is the idea that Rashid wouldn't know that most of these fall into that category. So... does him wondering if Harry is working for the bad guys imply multiple Outsider factions?
Im fairly confident that Rashid /knew/ precisely what the real deal with those events were (significantly more than Harry himself) and was only listing them to illustrate that from a certain
outside exterior perspective he looks awfully suspicious. Rashid ending that conversation with the cryptic "Not Yet your Time to Challenge the Council" bit cemented that idea for me.
Separately, regarding the possibility of Factions within the Outside: To the best of the Council's common Knowledge, Nope. That is specifically the only thing they Know, per CD:
“Creatures out of the Nevernever are a part of our reality, our universe. They can get pretty bizarre, but they have a membership card. Outsiders come from someplace else.”
[...]
I sighed. “That little creep Peabody dropped one Outsider on a meeting of the Council. The best wizards in the world were all in that one room and took it on together, and the thing still managed to murder a bunch of them. It’s hard to make magic stick to Outsiders. It’s hard to make them leave. It’s hard to hurt them. It’s hard to make them die. They’re insanely violent, insanely powerful, and just plain insane. But that isn’t what makes them dangerous.”
“Uh,” Thomas said. “It isn’t? Then what is?”
“They work together,” I said quietly. “Near as we can tell, they all work together.”
Thomas was silent for a moment as he considered the implications of that. “Work together,” he said. “To do what?”
I shook my head. “Whatever they do. Their actions are not always predicated on rationality—or at least, that’s what the Council thinks.”
Of course they can always be spectacularly wrong, particularly on this topic. Several of us have floated various theories for tunrcoat Outsiders hiding in plain sight in the mortal world (Mac, Mother Winter, The Blackstaff, The Gates themselves, Mac...)