1. Falmer servants.
If I'm not mistaken, this is the only place where Falmer have servants. Why is that? Why are they here and not everywhere else? And why are they here in the first place? How and why do the Falmer control them?
2. The Giant.
It's a pretty simple question, how did it get down there? I'm sure it did not make the long trek through Alftand. So why and how is it there?
3. The Silent City.
In Blackreach, as I'm sure most of you know, there is a pipe leading to a place known as the Silet City Catacombs. What is a city doing down there? Why is it silent?
I know that some of these questions may not have answers, but theories are very welcome. If I can form even the smallest bit of head canon here I would consider this endeavor a success.
Blackreach is a very curious place and I'm simply trying to figure it all out.