There's something really odd thing about the attack on Arctis Tor.
* Mab moves the bulk of her forces to the border with Summer, which pins Summer's forces in place to defend against a possible incursion from Winter which prevents Summer from retaliating against the Red Court for it's incursion into Faerie. (I'll get back to Mab later.)
* The Black Council appears to be in league with Outsiders.
* Somebody called up Outsiders to help the Red Court in it's battle with the White Council. Presumably these rogue wizards are members of the Black Council or at least it's magical foot soldiers.
* Nemfected Maeve works to gain Lily's trust. She helps Lily carry out a plan which allows Summer to strike a blow against the Red Court. This plan come to fruition because of Harry's assault on Arctis Tor to rescue Molly.
* The Black Council attack on Arctis Tor preceded Harry's rescue mission and even though it killed off Mab's troll bodyguard, overall that attack failed.
I don't think the Black Council attack was an attempt to free Nemfected Lea or to take out Mab. I don't think one denarian; even their best magic user, was enough to threaten Mab in her stronghold. (I'm assuming Thorned Namshiel had help, but he was the strongest player on the enemy team.) I think the attack was an attempt to do what Lily and Maeve later succeeded in doing, allow Summer to attack the Red Court. Specifically, I think they wanted Mab to recall her forces from the border with Summer so the Seelie Court could attack the Reds. I think the Black Council decided to nerf to Red Court so the war could drag on, and this would slowly degrade both the Reds and the White Council. I don't think they wanted either side to have any easy victory. Remember that in Dead Beat the White Council was in pretty bad shape. I suspect the Black Council and it's Outsider (allies? overlords?) buddies saw the Red Court much as Nicodemus did, "They're parasites who are inconvenient in the short term, dangerous in the middle distance, and fatal to any long-range plan."
The alternative is say that Nemfected Maeve was willing to allow Lily and the Summer Court to have their moment and help the White Council in it's war with the Reds, all so Maeve could completely gain Lily's confidence so that one day Maeve could bring about the downfall of both Summer and Winter. I suppose that's possible, but then it leaves the Black Council attack on Arctis Tor unexplained unless you really believe the BC thought they could storm Arctis Tor, which I find implausible. However, either explanation; my nerf the Red Court or Maeve's palace intrigue hypothesis, tells us the Black Council had no problem stabbing the Red Court in the back when it suited them. One more thing to consider is that nerfing the Red Court and helping Maeve worm her way into Lily confidence could have become duel goals to be carried out simultaneously. It could have went down this way; the Black Council attack fails to get Mab to draw her forces back from the border so a new and improved plan succeeds and helps nemfected Maeve at same time.
Just to make things more difficult to comprehend, there's a question no one seems to be asking and one that really needs to be answered in order to understand what actually happened. Why did Mab order her forces to the border with Summer in the first place? I used to think Mab made a deal not to attack the Red Court and help prevent Summer from doing so, but if this was the case, why did Maeve make it possible for Summer to attack the Reds? Do you see the contradiction here? Jim has been holding out some vital information which would allow us to untangle this puzzle.
P.S. You know, there's another explanation for why nemfected Maeve was willing to help Lily, but right now I'm too tired to type it out at the moment. I'll do it tomorrow.
See if this theory helps.
The Dead Beat events were a three-pronged end-game attack: Reds take out the Council, Maeve helps an attack on AT, and Cowl tries to ascend.
When Harry accidentally summons Mab to the lake in DB, Maeve & Co. take action. Maeve slows down time in AT (like she did in PG), causing the minutes Harry and Mab speak on Earth to be hours in AT. They attempt to free Lea, and destroy/damage the Winter wellspring in the process, thus weakening the defenders of the Gates.
After their conversation, Mab returns to find AT under assault. Even worse, she realizes that Maeve is helping, and therefore compromised.
Mab successfully repels the attackers, but realizes she's almost lost the game because she's now down three key pieces: her Lady, her Handmaiden, and her Knight. She's alone, her home has been attacked, and her daughter has been subverted by the enemy.
So what does she do?
She puts Winter on lockdown.
The borders are defended against any further intrusions. The offense offered by the Ramps (freely raiding through Fairie, almost as if they knew there'd be no reprisal) can wait. She has to concentrate on healing Lea, while suppressing her rage at Maeve's situation.
This explains why there was no retaliation against the Ramps between DB and PG, why Mab would be inactive for the PG fight at AT and would want to be alone, and how Mab finds out about Maeve.
In this light, the plot of PG becomes an unintended second raid on Arctis Tor using a pawn piece (Harry) that Mab wouldn't strike down (because she wants his Starborn power). It puts Harry there, where his godmother is being held. Scarecrow makes sure Harry strikes at the right place to weaken the bonds holding her, while simultaneously revealing her presence to him. (Although no-one thought he'd use Summer fire on the wellspring)
Had her treatment not progressed as far as it had, Nemesis could have promised him the world in return for freeing her, and he wouldn't have known who he was dealing with.
Then Mab would have been on the rooftop alone against an infected Lea and a misinformed Harry. She might have been forced to kill Lea, which would weaken her hold on Harry, and force her hand to try other, more desperate things to possess the starborn power.
In addition, the attack on the wellspring to free Lea (even without Summer fire) likely would have triggered the return of the defenders, thus completing the secondary part of the mission: convincing Lily that Maeve is on the side of good.