But when you think about it, other than Molly's mind-control stuff, is there any other Black Magic going on in Chicago? What exactly is the Gatekeeper trying to prevent?
I'm inclined to read what the Gatekeeper is trying to prevent is not Molly's fall because Molly is important, but the likely consequences for Harry's relationship to the Council if they execute Molly; that would fit with his explicitly warning Harry on that matter in TC. Dead Molly could easily mean berserk Harry having to be put down by Eb or Morgan, for example.
I've seen the various theories that they had some hold or bargain over Mab, or that maybe this was a strike to remove the Athame from Mab's possession (heck, I made that one myself at some point), but then this never really explained why Harry needed to come to Arctis Tor - the real attack was already defeated.
For completeness' sake, if we're summing up the options, I'd like to throw in another hypothesis:
The real "attack" on Winter is via the means of the athame, warping Mab and Lea, and possibly also via the means of Lea being required to make bargains that are not for Winter's good (like swapping the athame for Amoracchius in the first place). The Scarecrow a) has power entirely outside the nature of any of the other Fetches, which Harry identifies at the end of PG as "Black Council" modus operandi and b) has Harry's power fade out when it somes to near, in ways much more similar to Lord Raith's Outsider-backed immunity in BR than to just being too strong for it (cf. Ursiel in DM, "Grum" in SK). This leads me to suspect the Scarecrow is an Outsider-plus-allies agent who has the run of Arctis Tor.
The frontal assault by some Denarian - supposedly Namshiel though Mab avoids confirming this directly and makes great effort to distract Harry when he suggests it - is a rescue mission. The whole point is to blow away enough goblins and trolls that Harry and company have a hope of getting into Arctis Tor.
Mab's reason for going to such lengths to keep Harry in the dark about this ? Is that if he realised he could claim it as one of the favours he owes her paid.
- Madrigal is a known cats-paw for the BC. Someone invited him over a year before the convention started. Speculation is that he covering for **something**
Harry seems pretty clear that Madrigal is there as a distraction; a known fear-feeder to distract his attention from what the real phobophages are up to. We know that Lucius the Jann actually arranged that invitation for Madrigal, and I find the Scarecrow making a point of killing the unconscious Lucius rather than taking the advantage of surprise rather than using the advantage of surprise against any of its more dangerous foes also indicative of the Scarecrow's motivations.
Also, I'd say that technically we know Madrigal has links to the Circle alluded to in WN; whether this is the Circle alluded to in Changes, or the "Black Council". is entirely unproven.
that the general BC mode of operation is to give powerful-but-dangerous black magic tools to various people and let them run loose:
- Victor Sells
- Hexunwulf FBI
- Kravos
I think it's arguable whether any of those is let run loose at all, rather than attempts to lure Harry into something specific and totally different. Indeed, the deeper purpose for which Kravos is used is pretty solidly established in the text of GP.
1) Scarecrow is not that important to her that she wouldn't risk him in an attempt to gain something.
That seems a kind of weaker motivation than "Getting rid of Scarecrow
is important to her." I am not seeing why Mab would need to hide in disguise and do nothing unless Harry's actions there are both important and things she can't do directly. Mab does not strike me as someone who rolls dice.
Harry accidentally blows up the wellspring of Winter during the fight - wounding Mab (that's right, Harry wounded Mab, not the Hellfire attack), and calling back the hosts of Winter.
Oops...
I don't find that plausible because the results of it so very neatly punish the Reds for a transgression against Winter (and not Summer) in DB.
I bold-faced the part that I think implies that Harry's "pour Summer Fire into Winter's heart" was not by design.
I can see how you might read that that way, but to my mind that also works for a reading that being rid of the Scarecrow is what Mab needs Harry there for and trashing the Reds is a side-effect, though a very useful one.
- Lea attempts to bargain with Michael for Molly in PG.
Faerie wanting people's firstborn is a traditional bargaining chip, and Maeve asks for Harry's in SK, so I do not read this as likely very significant.
- Father Forthill's "hunch" at the end of PG -> it implies that the WG wanted Harry to teach Molly.
But remember that at the start of SmF Michael explicitly says that if he does not know who's behind what appears to him to be random good luck he will thank the WG for it. Michael, and to my mind Forthill as well, are philosophically inclined to credit any good they get to the WG, no matter who is actually behind it. (Some small part of me wants one day to see one of them misattribute something to the WG that is a beneficial act of, say, Odin, and then have them called before Odin to answer for that insult. But then I'm mean that way.)