Answer:
It holds most knowledge that has ever been said. But is not the brain, is not the head. To feathers and their masters, it's both bane and boonΒ One empty, and one full.
What is often returned, but never borrowed/
There is an ancient invention. Still used in some parts of the world today. That allows people to see through walls.
I follow the orders of only two. I respect the work of only two. I am in constant battles with many, Though one surpassed them all. With forces joined, We created hell, Until our mutual enemy fell. Who am I?
I usually wear a yellow coat. I usually have a dark head. I make marks wherever I go.
I am a animal that is cute but dangerous, what am I?