I was the subject of a great reward eventually given by a sarcastic computer program and apart of a famous phrase from an aristocrat. What am I?

I stand tall with walls of might, a royal home in a knight's sight.

Small and round, from golden grain, a copper in your hand remains.

I lay all day in the sun. A broken nose I have and a tail of a lion

When hoarded by one, I build prisons and lies. When shared among many, I help freedoms arise. I can forge heavy chains or can break them apart; The more you desire me, the less worthy your heart.