This worked. Before the population boom. Now without a Masquerade they'd have to stretch themselves thinner as the number of threats and potential ticking time bombs of many forms increases dramatically. They can only delegate so much.
Dresden was born during the population boom, and is coming to maturity as it begins to taper off.
The White Council would have seen it coming in the first place and lived through it. That we didnt see them do anything doesnt mean that they didnt do anything.
Always remember that Harry Dresden has a limited PoV.
Some of it is plot contrivance, some of it is ignorance, some of it is his being deliberately kept in the dark for IC reasons.
And Chicago is not necessarily representative of the rest of the setting.
Its definitely a stressor. I dont think anyone in authority has ever characterized it as a critical stressor.
...I'm pretty damn sure that Nemesis's plans to bring down the Masquerade is at least partially in aid of keeping the WC and their assets more occupied so it can pursue its goals with greater ease.
If the Masquerade came down humans might react to wizards in a negative way which means governments could be encouraged to take action. With orgs like the Black Council especially they likely wouldn't go through the effort when it could backfire on them too. They benefit from the environment a Masquerade produces. It's described as the nuclear option by Dresden in canon for a reason.
One Wizard putting his info in the phone book is not a threat to the Masquerade. Especially not with organizations like the Library of Congress existing and humans being willfully ignorant of such topics. Notice that most people don't take Dresden's claim to being a wizards seriously. They certainly aren't going to look at a page in a phone-book and think differently.
Im not.
We get that entire speech in Battle Grounds about why it engineered the Invasion of Chicago, and the Masquerade didnt crop up once as a target or a goal. The Accords are mentioned as a target, and stoking mortal fear as a goal, but the Masquerade in and of itself doesnt get a mention.
Now it could be lying, because Nemesis, but we have no way of knowing one way or the other.
What we know: Nemesis goals are to bring down the Outer Gates and wipe out everything. Empty Night.
And Nemesis itself dates back to before there was a Masquerade; it knows damn well that the existence of a Masquerade has little bearing on the Gates themselves.
Sociopolitical instability will help its goals, and its something it appears to actively pursue when it can, but the Masquerade, or the absence thereof? Not really.
Similarly, it bears pointing out that the Outsider-backed coup attempt in the White Court was based around an intent to go after lesser human magic users and their mothers/potential mothers.
Whatever Nemesis' plans are, the use of mortal magic-users is not one of them.
The White Council doesn't just concern themselves with the seriously magically talented. They go through some effort to police/handle humans who abuse magic if things get out of hand and make attempts to stop that from happening. Increased deployments for such matters means increased casualties.
We also have to factor in how their enemies will react to their attention being split even further. Outsiders and demons for example would have an easier time getting people to summon them if the public was aware that summoning is possible with the knowhow. You don't have to be particularly powerful to try summoning something.
Considering the current spy issue, along with their war, I'm not seeing how they could effectively handle the much greater workload and avoid creating openings that their enemies would take advantage of with a great degree of success. Unless they completely cut themselves off the movements of humanity will always effect them greatly, as the Salem witch trails would attest to.
1) Yes. But the progressive nature of black magic appears to be that most users cant but make themselves obvious.
Note that we havent seen any of the elder wizards talk about this as a concern. Just Harry, who lives in one city in one part of the world, and who doesnt even have a fragment of the full picture. I have to wonder if its actually the issue he thinks elsewhere, in other parts of the world where belief in the supernatural is much closer to the surface.
RL? I knew places in Southeast and Southwest Nigeria where you could allegedly go to find witch doctors and shaman who could make you magically bulletproof, or spells for fortune, or magically attractive to the opposite sex.
And in Swaziland/Eswatini, there are air traffic regulations for flying wizards.
In the Dresdenverse, a fair number of these wont be charlatans.
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2) Its worth remembering that a lot of evil factions dont want mortal magic users either, and arent going to tolerate startups or independents around them.
Duke Paolo Ortega of the Outsider-aligned Red Court, Arianna's husband was a Brazilian professor who spent a lot of his time explicitly going around trying to debunk the existence of magic; Harry met him on Not!Jerry Springer when he was debunking the existence of magic. Again.
The Fomor would simply chuck them into a vat to make more magical supersoldiers or constructs.
And even evil human factions will happily fuck each other over.
See Storm Front, where the black mage who trained Victor Sells deliberately trained him incompletely, without basic lessons. Or Fool Moon, where the FBI hexenwulfen summarily murdered the biker lycanthropes as soon as they got the opportunity.
Destro often doesnt cooperate very well. Or tolerate competition.
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3) *shrug*
Have they suffered losses? Sure. Serious losses, even; the Wardens were devastated.
Have they suffered existential losses? No.
I think you are very much underestimating their capabilities. Or the reach of the network of allies they have cultivated for centuries, most of whom we never see onscreen. The Venator Umborum, the Church, the temple networks out in Asia, the kenku....they only get brief asides in the books, but they do exist. As do the heavy hitters like Odin.
The Salem witch trials didnt do anything to the wizarding community. It killed at least 41 people, at least 28 of them women.
Its an example of the sociopolitical instability I was talking about, because almost nobody in that community would have been a serious magic-user, assuming there were any magic-users among them.
Thats why they were vulnerable enough to be hung by yokels.
Its not that wizards are immune, mind; Etienne the Enchanter died at the stake in Paris.
But when persecution is going on, the people who can shield, go invisible and step out into the NeverNever are very hard targets for any sort of bullshit, even without their breaking out offensive magic.