My thickness is no more than a few centimeters, yet my depth can span to infinity. Although mundane, I intimidate most animals. When in my presence, you will inevitably follow me. What am I?
It is mirror
I shift around, though always slowly. I never move more than a few inches at a time. A large movement by me can kill many people. I am huge, yet unseen by humans. What am I?
Although I am important to you, I am but a mere illusion. My beginning is as unknown as my conclusion. The more that you think, the more that I appear to pass. When you are in pleasure, I tend to escape your grasp. What am I?
Looking at my face, I'm no more than six.
Look at the rest of me and I'm 21.
You'll see my twin and me in Las Vegas.
Say my name and you'd be uttering a threat.
What am I?