Ok, I can see why this game can be addictive. I finally got around to buying it and started playing a little while ago.
Spent my first night in a nice little hole I dug in the mountain to get some stone. It was starting to get dark, so I sat back and watched... things starting to move around in the distance. And make noise. I plopped down some of the stone I had to seal off the entrance and continued to watch though the little opening over the naturally dug hole in front of my little cave
And then something dropped down the hole right in front me and scared the crap out of me!
I stayed as still as I could the rest of the night.
Finally, light started coming, so I decided to see what had scared the crap out of me earlier. And ended up falling down the hole right in front of it. It then proceeded to quickly and efficiently kill me.