I like the story so far but thought I would point out one thing. I t is an extremely unlikely event that Gringotts Goblins would steal or embezzle from one of there costumers vaults. Evan though Goblins are not trusted in most things in the world of Harry Potter they do have a code that binds them to act in a certain fashion. More to the point with their reputation if it became known that they had been a part of what happened in this chapter than they would no longer have a single wizarding customer. Also I think most of the wizarding world would no longer tolerate the presence of goblins. Its just my opinion that this part is unrealistic even in your darker alternate reality. my apologies if this seems over critical as that is not my intention. I am just trying to offer some constructive criticism.
Author's response
I get that I went over the top in reversing the 'helpful goblins' trope that was such a common and ridiculous theme when I was writing this back in the day. Even so, the goblins were collaborating with greedy purebloods, so a lot of their manipulations are, strictly speaking, perfectly legal. Much of the protections and contract laws developed in the muggle world have yet to seep into Ministry laws, so the economic model is closer to the pre-Depression monopolies of the nineteenth century. This is obviously a departure from canon, but not a completely unbelievable one, I hope.