Fascinating idea, but I don't think it's the moment of conception, as Con stated above. Harry's guitar playing at the end of White Night is after Lash died, but clearly shows another presence in his head almost immediately after her death. But it seems safe to assume that Jim was deliberately foreshadowing, and that perhaps Bonnie helped put that idea into Harry's head, as a way to prepare him / make her presence known.

Actually, I think Id Harry is a better candidate for putting that thought in Harry's mind. Id Harry knows all about Bonnie, and it's well established that he's responsible for a lot of Harry's intuition. Even if conscious Harry didn't get it at the time, it was a good way to prime him.

See, and what I'm picturing is the opposite.  I'm picturing that once they are sufficiently forgotten, they disappear out of the well.  Eventually leaving a depression where a new inmate could be place.

Fascinating idea. Could be. That theory would mean that everything in there right now, all 12 (or 13) hallways worth of beasties are still known on Earth. In that case, either the previous wardens were very busy adding inmates, or it takes geologic levels of time for these things to be "sufficiently forgotten."

For story-telling reasons, it makes a lot more sense for the White Council and Winter to not be aligned. So many more options for making things hard on Harry that way.

I think it would be very interesting indeed if the Merlin had Harry as his ace in the hole.  That implies all sorts of changes in the council and the Merlin.   I would argue that up to this point the Merlin has never looked at Harry as anything more than a annoyance, a dangerous warlock or a lever to use against other senior council members.  The Merlin has certainly been petty with regards to Harry, he has not devoted much energy to opposing Harry beyond petty political games.  While the books are harry centric, the Merlin has shown no indication of being harry centric. 

Also, if the Merlin's plans involved Harry in some significant way, then the Merlin plans to disrupt the peace talks in some significant way.  The Merlin has always seen harry as a force of destruction/chaos/disruption.   If the Merlin sees benefit in Harry's involvement, then he wants the Peace talks disrupted.   Otherwise the Merlin's plans for Harry would all be about how to keep Harry away from the Peace Talks.   Why do you imagine the Merlin wants the talks to fail?

I think the argument for Harry being the Merlin's ace-in-the-hole is primarily Doylist. From Jim's perspective, the reason to build a book around a concept like a summit is to play with Harry's now divided loyalties. It's rich with compelling story options which force Harry to choose sides in uncomfortable ways that may have serious consequences. As for an in-universe rationale, Harry has been accruing power at an alarming rate. Remember, the last time we heard anything out of the Merlin was the beginning of Changes, before Harry's Winter Knighthood, before the fall of the Reds, and before Harry had any understanding of what it meant to take Demonreach as his sanctum. He's not the small fry he was last time we checked in with the WCW.

The peace talks are about resolving the war with the Red Court, Black Court and White court.  I agree with you that this war is effectively over, but it is NOT actually over.   The black and white courts were active participants in the war and they are not destroyed. 

I do agree that the primary focus of the peace talks themselves are the spoils/territory to be divided and managing the conflicts already happening as supernatural races fight over the spoils.  Simply ending the war would be fairly easy as the Black and Red would just keep what they got and return to the status quo.  It is all the red territory that is now up for grabs that is the problem -- especially as the White Council is not capable/willing of taking it for themselves and defend it against all comers -- and winter/summer do not want it.

The WCW's inability to defend all of this now-exposed territory is why I feel like the Merlin might be willing to trade away the safety of some portion of the vanilla mortals and lower talents for peace. The Merlin is nothing if not a cold, political pragmatist, a lot like Mab in that way. The Merlin needs time to rebuilt his ranks, and he needs safety for his membership first and foremost. They simply aren't strong enough to properly defend mankind right now, and everyone knows it. Best to retreat, cede some territory, and rebuilt their strength. And besides, that stance is a great way to put more tension between him and Harry right from the start, and Jim just loves that sort of thing.

I disagree that there will be just two clear factions plus the fence sitters. The known signatories of the Accords are:

The Archive (both an emissary and a Freeholding Lord)
The Denarians - Nicodemus Archleone no longer a signatory as of Skin Game
Donar Vadderung, CEO of Monoc Securities
Both Faerie Courts
John Marcone (the first non-supernatural to sign onto the Accords)
Vampire Courts
The White Council
The Svartalves
Drakul
A semi-immortal shapshifter guru in Ukraine
Two Dragons
The Fomor

We know the Fomor called this meeting. No one really likes like Fomor, expect maybe the BCV and some of the immortal creatures we've barely met, maybe. The Fae exiled them to begin with, they've pissed off the Svartalves (Bombshells), WCV and Marcone (Even Hand, Aftermath), and the WCW. I'm confident Vadderung and the Archive aren't fans. They've taken all of the Reds old territory, I'm sure they're just fine with that.

Now, if those are your battle lines, I see where you're coming from. But everyone on that large side has wildly different interests regarding everything else. I really don't see nice even factions developing, even if the Fomor are that polarizing.

Therefore it's entirely possible that he's referring to ....
And their relentless pursuit of late fees.

No, anything but that!

More seriously though, I was just being cute before when I said Griffyn612's summary of "what stalks us all" reminded me of "Empty Night."  But as I think about it, I think that may be the honest correct answer, the summary of all the candidates proposed. "Empty night" is the favorite curse of the WCV, but it had one other very prominent appearance, on the lips of none other than Mother Summer:

"Ah, yes. I see," Mother Summer said. "So many new futures unwinding."
"Too many bright ones," Mother Winter said sullenly.
"Even you must think better that than empty night."
Mother Winter spit to one side.

This conversation was brought on by Harry learning of Nemesis. This change brought on the possibly many bright possible futures, and apparently was a blow against "empty night" coming to pass.  We also have this quote from Mab, in CH:

"I am Mab. The stars will rain from the sky before Mab fulfills not her word."

It isn't a big leap to say that Mab has given her word to protect our reality from Outsiders. The consequence of failing that, an Outsider invasion, would put out the stars in the sky, unmake our existence as we know it. That is the known goal of Nemesis, bringing on this "empty night." That phrase is shorthand for the horrible apocalypse that would befall us if Mab failed to keep her word and safeguard reality.

So, when Lea said  “I grew too arrogant with the power I held. I thought I could overcome what stalks us all. Foolish." she means she thought she could prevent empty night all on her own. I had been playing with the idea that perhaps Lea attempted something more overtly pro-outsider, but I think I've been talked out of that. Nemesis doesn't seem to work that way, anyway. It seems more to encourage a being to take their desires further than is rational, and to allow them to overcome foundational rules, such as a fae lying. Lea has shown several times that she has the impulse to try and overcome Mab, to "take the lead." Their relationship is one of slightly mismatched rivals. She even goes into detail on the topic in GS:

"In all of winter, I am second in power only to Mab. Which she has allowed because I have incurred with it proportionate obligation to her. She is my dearest enemy, but even I do not owe Mab so much..."
My godmother was what she was, a being of violence, deceit and a thirst for power... and believe me, if Lea had been the high priestess of murder, blood lust, scheming and manipulation, then Mab was the goddess my godmother worshiped. Come to think of it, that was probably an apt description of their relationship.

Lea's statement could be read that she tried to overcome Nemesis on her own. Or a simple overstepping of bounds, speaking out of turn or making a decision without consulting Mab first. It could also mean she interfered beyond her station in the war with the Outsiders. Maybe even an action that might have eventually led to Mab's ouster, similar to Maeve's goals.  But unlike Maeve, she became self-conscious of the change within herself, and recognized it as a problem, perhaps she even knew it was Nemesis. And so she went to Mab.

It's quite clear looking at Harry's memories with Justin that he was trying to go with old-school indoctrination at first- which is kinda a waste of time if you're just gonna mind-jack them.

Something must have happened to accelerate his plans...

I agree, enthralling them doesn't square with the rest of his time with Harry. Given that he was a known associate of Margaret, I don't buy the "flipped a switch" reasoning. Something bumping up the time tables makes more sense. The fact that the HWWB ritual is on a clock strikes me as relevant.