Harry is in a funk all breakfast.
"How do I profit off being a Dark Lord over them while losing? What do I extract?"
"If I become a Dark Lord, and conquer the wizarding governments of the New World, I will lead the settlers, the immigrants to the New World, to defeat, to lose ownership of the land. For the settlers to return back to Europe and the immigrants to leave. The only thing left is a memory of that glorious time."
Under Harry's Dark Lordship, reservations will have to find some form of cohesion by rebelling against the productive vices of him or face dissolution. And even reservations that become countries, they will be occupied by Harry's Dark Forces, if he lives long enough.
During his lunch break, Harry stays up in the library reading about the natives. The more he reads about them, the more he is convinced another Dark Lord has intervened.
The reservations are like being locked up in a cell. An unknown Dark Lord, one that has survived for centuries, must have set them aside. The settlers, in all common sense, should have killed off the natives. That is how it used to be done. But a Dark Lord must have intervened, and placed them in cells; the reservations.
A Dark Lord is awaiting for the chance to have them get back their freedom by rebelling against the Dark Lord's vices. Something that will provide cohesion to them. This is like a duel between a Dark Lord and a hero.
Some natives, caged in their reservations, will just end up joining the Dark Lord. These are the reservations that dissolve. Others will become countries, while some will still sit in their cells.
But who is this New World Dark Lord that has been afflicting the natives for centuries?
The time period is the answer. Any wizard that has lived for centuries are top candidates.
Harry went to the genealogy section, and looked up the oldest living wizards.
Only two wizards stood out: Nicolas Flamel and his wife at over six hundred years old.
All Harry knows, is that if they are Dark Lords: they have a burning desire to fail, to prevent dead weight from following them.
A Dark Lord always fails because they fear being exploited by dead weight followers.
This New World Dark Lord is preparing to fail, to be overthrown by the natives. But if the natives overthrow him by doing their own productive vices, they will be squashed, like a rebellion. Only an unique unduplicable solution that inspires faith can be used.
Harry knew how he would act as a Dark Lord. He would set it up so that the only way the natives could defeat him is by claiming the underground as their land. Everything that is deeply underground (at least below basement level) would be theirs to claim. But just as there are reservations on the service, there are pockets of ownership of the settlers in the underground.
This is how it is for the ecumenopolis, where those that live deep down are exploited by those that live on the top. Might as well make it official.
Harry thus has his own defeat planned out. He will fail by natives taking the underground, and negotiating with the above ground for exchanges.