What You Need to Know About Blood Magic
Blood magic is dangerous. The sorcerer or sorceress uses the power that is found within the physical substance that is the blood. With this power he or she shapes into reality what has formed inside his or her mind. This requires a great deal of force to impose your will upon the world and enough self-discipline to the master the subtleties of such arcane lore. Most importantly, it requires enough willingness to use the potency of the blood itself. A sorceress that would tap into the blood must break free from the social and cultural beliefs in order to fully explore the potential of magic.
Blood magic can be flashy. It can be used to withdraw the life energies from others, curse them with disease or even clean and heal their sickness. Blood magic can also be incredibly subtle. Reforming the world to bend to your will requires more than just flash. It takes time, effort, determination and transformation of the subtle forms that reside deep within the essence of all things. Blood magic intends to create a state of control over the self and the world around you. To remove anything that prevents you from fulfilling what you most desire.
High and low blood magic are simply distinctions between ritual magic (high blood magic) and non-ritual magic (low blood magic).
High blood magic is magic that is enhanced by ritual and the use of blood during that ritual. By using the essences that reside within blood, the sorceress is able to heighten the act of the ritual when in turn adds greater power to the spell itself. Without it, the spell is no greater or lesser than any other spell. With it, the spell is charged with an unparalleled amount of energy. Because of this, the sorceress is able to use her own maximum power, the power of the ritual itself and the power residing within the blood. These things combine to exponentially increase the potency of any spell. Spells of this nature are difficult and powerful, allowing those with sufficient discipline, patience and power to achieve incredibly potent and powerful results.
Low blood magic is direct magic, the sorcerer's intentions manifest themselves into immediate results with little or no preparation. A sorceress who is an adept might cast a spell and use an aggressive hand gesture to provide some personal component to her spell.
The old adage of "like to like" applies here. We all are human and all share blood so there is already a link. There is no need for complex and time-consuming rituals the majority of the time. When you start thinking in this manner you are more able to cast quite effective spells on anyone or anything in spite of any shielding or naturally occurring defenses.
Low blood magic operates on the sympathy principle. If one looks at it as though we all share a common link because we are all human, the connection is made.
One could call blood magic just a form of basic life magic. So a sorceress could use blood, any blood, to form the sympathetic connection to any other target. Of course the more similar the blood being used is to that target the more effective the spell is going to be.