Good points, all. Fiendfyre seems robust.

I might counter that most combat magic, even the adult sort, seems to be line-of-sight, which is a huge handicap. It also seems to be very inaccurate. If Harry & Co can literally dodge Deatheaters on foot and brooms, supersonic jets and HALO insertions are going to be really hard to target. Not to mention artillery shells in flight. And Wizards seem weirdly resistant to (biased against?) using magical heavy weapons or fire team tactics. They have a real duelist mentality.

But the ability to erase from time does really trump. I concede.

IS.

Am I the only one with the feeling that it's just too easy, too fast ? Harry uniting all of Hogwarts and most of Magical Britain, despite generation old hostilities, remaining hatred from a war that only ended 10 years ago, personal quarrels, and frontal opposition in terminal values (I don't see how persons sharing Dumbledore ethics can so easily accept to side with wizards who just voted to torture to death a 11yo girl, nor how blood purists can easily side with muggleborn).

I can get Harry, the ultra-rational boy who wants to save Hermione at all cost putting back his rightful horror at siding with people who voted to send her to Azkhaban, but I just can't see how the whole magical Britain letting aside their personal quarrels, hatred, and value conflicts that easily, just for one death, especially since "that still made Hogwarts safer than Beauxbatons, let alone Durmstrang".

Jokes's on Harry, by the time he revives Hermione, the difference in maturity level will make a continued friendship impossible.

I think that people may be confused as to what's happening with this announcement.

The early phase details of the agreement were negotiated first between Harry and Lucius. Harry represented house Potter here because he's the entirety of house Potter. Lucius negotiated with Harry because Harry (as the boy who lived) has a lot of clout and credibility and he offered to throw that behind Draco. On an emotional level, HP also offers revenge against whoever attacked Draco and the possibility of revenge against Dumbledore.

Step two, the adults negotiate amongst themselves. In this second phase Lucius goes to the board of Governors with the agreement he and Harry made as a starting point.

The Knott and Greengrass votes are naturally inclined to go with Malfoy by faction alliance. Knott is also incentivized to go with the plan for other reasons. His son is a friend and chief lieutenant of Harry Potter. That's a potentially very valuable connection, but its a connection that can't be used when the votes are split death eater v Dumbledore. Realignment effectively "monetized" that asset. Greengrass doesn't have that and so asks for a few sweeteners on its deal. Also, the plan reduces their children's risk of death which is a non trivial inducement.

Bones runs the aurors. That's a strong base, but the aurors are generally kept out of Hogwarts, which was previously described as an invincible fortress. This puts her people inside Hogwarts which expands her domain of influence. While she probably wouldn't be willing to do that at the expense of being kicked from the order faction to the death eater faction, its worth it if she gets to keep most of the same allies (which she does via Harry) while isolating Juergen and other of her more extreme opponents. Also, the plan reduces the childrens' risk of death which is a non trivial inducement.

Neville inherits the Longbottom vote when he turns 18, so Longbottom is in Harry's camp in the long run and so his aunt has reason to at least reap the benefits of being on Harry's side since they pay the costs regardless. Like Bones she benefits from isolating extremists like Juergen. Based on her comments in prior chapters both at the war game and about QQs speech she favors a higher level of military readiness and is getting that from this deal.

So once the adults agree on the deal. Why announce it this way vs some other way?

An announcement through official channels goes through Dumbledore. Bypassing that contributes to sidelining / undermining Dumbledore, so Malfoy has a clear interest in the announcement through non official channels.

For Bones and Longbottom an announcement from the board has the two of them seen as going along with house Malfoy. Given their current alliances this would be damaging and bad for their images. By having the children give the boards's announcement right on the heel of an announcement by Harry and Draco the optics are that Draco is bringing the Greengrass / Knott votes and Harry is bringing the Bones / Longbottom votes. This allows them to maintain the optics of their factional alliance. They are seen as Harry's votes rather than as Malfoys votes.

Greengrass and Knott are in similar situations. As parts of Malfoys faction they also benefit from sidelining Dumbledore. They are lesser houses than Malfoy and are voting with Malfoy and are seen to be voting with Malfoy. Their houses get much more visibility and 'airtime' with this plan than if the board announced a vote. The chapter notes that it had all been negotiated and rehearsed and that the prominent role Daphne got was one of the carrots thrown to Greengrass.

Basically it happens this way because it is in the parents interests for it to happen this way.

Fulminated mercury.

Edited to add: Sorry, been rewatching old Breaking Bad. You'd have to trick them into chewing it or something, wouldn't you?

And bear in mind that sulfuric acid is only one possibility among several!

Liquid oxygen, which is also pretty easy to produce or acquire, expands quite a bit when it evaporates, and rapidly oxidizes all of your pretty organic chemistry. If you could ship enough liquid oxygen (transfigured into something else) inside a human, they would burn and explode when the transfiguration wears off.

Botulinum toxin was also mentioned in the fic and is the weapon of choice for DIY genocide.

Pyrophoric substances, transfigured and then finely ground, will start burning in an oxygen-containing atmosphere.

Obtain nuclear weapons material (the hard part) and transfigure several subcritical pieces into iron, assemble them to give one large ball, drop it (or bury it underground), and run.

Certainly not all of these are practical, but all of them sound awesome.

Telling the troll to eat her feet first so that the emergency portkey does not work?

To be fair, it ate her legs, not just her feet. It seems likely enough that if a troll is trying to kill you, it might as well eat your legs as any other part of you.

On the other hand...

The powerful and enigmatic Defense Professor was 'resting' or whatever-the-heck-was-wrong-with-him, his hands making fumbling, hesitant grabs at a chicken-leg that seemed to be eluding him on the plate.

So it's Dumbledore who's the sexist fridger, not Eliezer!

I realise you're probably just being flippant, but I should note that Hermione is the only person Dumbledore knows and has access to that really matters to Harry. If he was going to fridge anyone, it would be her, for that reason rather than sexist ones.

I don't think this is historically true. Humans actively traded since paleolithic times (there are archeological finds like amber far away inland or stone tools made out of stone that does not occur anywhere locally).

Merchants were typically seen as of lower status than the nobles and the military (for rather obvious reasons), but of higher status than craftsmen and peasants.