So I was wandering around Blackreach and I came across a Giant, just walking around, scratching his back, doing his own thing. So I have 2 questions

1.Are Giants supposed to be down there
2. How did it get down there?

Also while I was following him, I decided to unleash a Centurion on him, the Giant destroyed it and then went on his way. I haven't been able to find him since, whether he was killed by Falmer or what...

There is a little of everything down there.

And in case you didn't know: use unrelenting force on the big yellow orb.

1. He's meant to be down there. I found him in my first trip into Blackreach - he crushed my flame atronach, but didn't bother me in the slightest.

2. No idea. Perhaps he was a Dwemer's pet?

I was wondering that as well when I was down there. The weirdest part is...he just looked at me when I walked up to him.

What BIG YELLOW Orb?