I’m surprised Harkon didn’t try to take Blackreach for himself. They’re immune to Falmer poison, they can use their full power without sunlight, they’re smarter and have access to invisibility, illusions, and charms.
In return he could have a country sized cavern, with at least two points of contact to Skyrim one either end, all the dwemer tech to hoard and use with their ancient knowledge. He could subjugate the falmer to be blood livestock, they’re already crafted to be good slaves by the dwemer.
He could slowly build up a vampire/thrall/dwemer machine army right under Skyrim then wage war overnight. Could even use dwemer machines by day to maintain territory until you complete this master prophecy you have.
I’m still young at 25, but I can see the hallmarks of aging. I’ve moved to a new state for 5 years now and when I visited my old home it felt half foreign, half familiar. I’m the youngest so my mom’s age is starting to show.
Things I consider recent are now described as “years ago”. I’m seeing things evolve through life. Things that felt like they had a beginning, middle, end now are starting up again. Almost like a ride that’s resetting for the next ones in line.