Yes the blood is central. The blood sacrifice is both holders of mana (it is a Polynesian concept) and a way to manipulate mana for the purposes of seeing the physical result that is magic, answered prayers, favorable luck, etc. etc. etc. Blood is power and in the series, regardless of how blood is taken it still results in power acquisition or loss of power which are two sides of one coin. Take Varys and Tyrion's conversation on power. I have colored coded which instances of power. Knowled