It never really made sense to me either. If he wanted loyal enforcers, it would've been far easier to manipulate and brainwash than to enthrall them. Hell, if he had just ASKED Harry to help him, he probably would have, right up until he put Elaine in a brainlock. And his move against Harry involves a straitjacket rather than magic for some reason? The whole thing just doesn't make a whole lot of sense, and seems like stupidity on Justin's part—and I never assume stupidity where wizards are concerned.

The straitjacket calls to mind Thomas' bonds in BR. Maybe Harry was to be the sacrifice in the ritual? Justin was skilled enough to perform two of the roles in the summoning, with Elaine thralled into doing the third, perhaps.

As I recall, there hasn't been much of anything even mentioned about the physical gem since Changes.

It is mentioned in CD that Mab had it properly set into the Pentacle necklace by a jeweler of some sort, as opposed to the ugly epoxy job Harry did on-the-fly in CH. But you're right, he hasn't had to use it since. One more piece of gear not living up to it's potential. I suppose the past two stories were pretty Chicago-centric, but Harry probably could have checked out the possible ritual locations in CD himself, instead of using the Guard.

Jim has said that the scale of these stories will be going up geographically as we draw closer to the BAT. That's the reason for introducing Tilly and seeding the idea that Lara has Congressmen under her sway. I imagine Harry will have more cause to use the Ways as things progress.

"Potential Wizards" seems to be a much broader category than "Potential Starborns." While we still don't know everything involved, Lash's line from White Night seems to suggest there is more to it than just Wizard parentage and the right birthday:

"It is relevant," Lasciel said, "because of the circumstances of your birth -- because of why you were born, Harry.  Your mother found the strength to escape Lord Raith for a reason."
What the hell was she talking about?
Thud-thump: 1:26.
"There was a complex confluence of events, of energies, of circumstances that would have given a child born under them the potential to wield power over Outsiders."

It's my read that it would only be achieved deliberately, that accidentally / coincidentally creating a starborn is highly unlikely. Hence, Justin probably had something to do with it. He was almost certainly aware of Harry being created towards that purpose, perhaps even involved in the original plan to do it.

I believe that Margaret DID know of the need for a Starborn.  I don't believe that Thomas was her first attempt.  It think she was just enjoying great sex.

But, it's entirely possible that she learned of the need, and maybe the process, for creating a Starborn, from Pappa Raith's library.  And then she started working on a means of escape.

Further, I believe that Justin was in on the plan. 

Here's a further WAG ... Margart was trying to get the Vampire courts together to take over the outer gates.

I don't think she ran off WITH Malcolm.  I think she met him while on the run.

I think she was trying to create a starborn with LR.  She told Eb that she was with LR to accomplish something, that they had a plan.

I think it more likely that Elaine's parents didn't know, but someone (Justin) saw the circumstances of her birth and figured it was possible.  He then killed the parents and arranged to become the foster parent.  IIRC he adopted Harry for pretty much the same reason.

In Blood Rights Ch 35, Eb clarifies a few of these details:

I don't know why, but for some reason she turned away from her previous associates, including Justin DuMorne. After that, no where was safe for her. She ran, from her former allies and from the wardens for perhaps two years... She met your father. A man, a mortal without powers, without influence, without resources, but a man with a good soul like few I have ever seen. I believe she fell in love with him.

Combined with what Eb tells about the dinner with Margaret, Lord Raith, Ariana and himself in the last chapter of Changes, we can infer a few facts:

• The attempt to conceive a starborn was a deliberate plan involving, at a minimum Lord Raith and Ariana. Justin was also a likely co-conspirator.
• She met Malcolm after leaving Lord Raith, not before. Which isn't to say she didn't deliberately seek out a man with a "good soul."

In DuMorne, Raith, and Ariana of RCV, we have three known Outsider associates. Whether the starborn plan originated from one of them or from Margaret, it seems likely that learning of their Outsider associations / plans for her potential child were what drove her away. Leaving Thomas behind means she didn't leave simply out of mother's love / "You won't harm my baby," so it's more likely she left with the deliberate purpose in mind to subvert their pro-Outsider agenda. It is possible / reasonable to think she thought out someone like Malcolm for just that end. Or maybe the father didn't factor in, hard to say. The conversation with Malcolm in Dead Beat suggests he's at least in on the plan post-mortum, but there's no evidence either way if he had knowledge of it before his death.

The assumption that this triumvirate had something to do with Malcolm's death is reasonable. What I am curious about is if Elaine was known to the rest of the group, or only Justin. And if she was similarly cultivated, or just come upon by Justin?

You can make a distinction between what Lea did on her own and what Lea did under influence of Nemesis but one does not have to. Everything Lea did under influence of Nemesis she still did and some of that was a chalenge of Mab's authority.

I agree, it remains unclear how much being Nfected is an usurpation of a being's will versus a more subtle influence on one's thoughts and actions. Though, by Mr. Sunshine's rules, both are equally problematic.

I have no doubt Mab was referring to Lea when she said "she" challenged her authority.  But a challenge to Mab's authority does not require open rebellion.  Lea attempting to act without Mab's consent is a challenge of her authority.  Lea acting in Mab's interest in a way Mab wouldn't approve of is a challenge of her authority.

The text tells us Lea tried to do something against an enemy too powerful for her, she turned herself in to Mab, and Mab helped heal her while reasserting her authority over such things.

I think Griffyn612 has the right idea. What I want to think about further is what Arjan brought up, what did Lea mean by "what stalks us all."

With hindsight I translate "What stalks us all" as Nemesis. Lea tried to overcome it herself but failed. Ashamed she went to her queen.

This reading makes sense to me, and strikes me as the most obvious interpretation. Lea tried to struggle against Nemesis on her own, but was unable to win the fight without help. But the struggle alone doesn't seem like the offense that Mab spoke of in Changes. So what was the action that Nemesis was attempting to cause Lea to perform? A simple, small action of verbal challenge, a simple questioning of Mab's orders would probably be enough to fit the bill, that's most likely.

But what if we think bigger? What if "I thought I could overcome what stalks us all" refers to death? That phrase is certainly a common motif of death. And the goal of vanquishing death is already held by Cowl (according to Kumori anyway), who provided the athame to Lea via Bianca. Lea would be in a position to potentially make some type of move against Mother Winter, who is the closest personification of "death" in the DV so far. And that would certainly qualify as a challenges to Mab's authority, an action against Mab's word and will. If Lea recovered herself and broke down in shame before she actually took an action, then everything fits.

What we know and what we infer are two vastly different things fyi. That's not known. We know they last talked at Hastings, and a few other things iirc, but not that itself. It's a probably accurately surmised though.

Fair, I may have been layering WOJs or fan theory on top of my recollection of the text. I can do a bit of poking around to see how much about Hastings is in the text vs WOJ vs theory. Regardless, it's significance in the lore of the DV is established and likely to increase.