Answer:
I'm sometimes white but most often I'm black. I take you there but never bring you back.
In a tunnel of darkness lies a beast of iron. I can only attack when pulled back. What am I?
My geometry is lost in the night to be found in daylight's break. The rigors of time have torn me to shreds, yet I stand to protect that which lies within. What am I?
You throw me out when you use me and take me in when you are done.
I am shared by goats devils and unicorns.
What made Cyclops quit teaching?