Answer:
The 8 of us go forth and back to protect our king from a foes attack
I fill a room but take no space. What am I?
I must be broken before you can use me.
Deep, deep, do they go. Spreading out as they go. Never needing any air. They are sometimes as fine as hair.
I am needed for most animals and hardcover books. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.