The Abattoir
Ran by The Oy’uz, generations of ponies lived and died there without leaving it’s labyrinthian walls. They continue their secretive work there undisturbed, even by any of the changes that have happened to the city. Apparently this is where Ambrosia is refined and where Hoarders are made and trained.
You do not know much more about this place and it seems like pretty much no one else does either due to it’s secrecy. Although you’ve heard a few odd things: For one, they apparently are the only place in the city that are not infertile due to Ambrosia’s side effects. They also are pioneers of so called secret techniques that they are forbidden from teaching to the outside world. They see Carcasse as a completely separate civilization to their own.
It’s also possible to be permanently banished from The Abattoir, branded an Exile. They carve sealing tattoos on their Exiles, each preventing them from speaking of a secret they know, and which scar them for the rest of their life. They then turn them over to The Kuvava and have them decide if they want them to live in Carcasse. Unless they’ve done something completely unforgivable, they are usually granted right to live in Carcasse as they are allowed to use their Skills in the city and prove very useful. So far the only Exile you know is Mutual Exchange.