Answer:
Men seize me from my home tear apart my flesh drink the sweet blood then cast my skin aside.
Two in a whole and four in a pair. Six in a trio you see. Eight's a quartet but what you must get is the name that fits just one of me.
What gets sharper the more you use it?
I am easy to see but no one likes looking at me. Without me there would be no you. I can make you complain or make you happy. But you almost always take me for-granted.
I can be cracked made told and played.
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.