Here's a Blood Magic path for Low Magic, too!
An apprentice blood mage learns no true magic at the beginning, but instead focuses on learning about the circulation and use of blood, differentiation of various types, its properties both mundane and mystical, and the anatomy of the body. This acts as a Fact towards anything involving blood.
The adepts learn the subtle art of controlling and channeling blood, whether to cause harm (1d6) or to prevent someone from bleeding out, including themselves. Adepts are taught to bolster their own vital force through a suitable sacrifice, giving them 4 temporary hit points or hit dice that disappear after a day if not used. An adept can instantly tell what a creature is by tasting their blood, and even a particular specific one if they’ve tasted their blood before.
A master of blood magic can severely damage an enemy by boiling their blood (1d10), track a victim unerringly simply by possessing a drop of their blood as a single use arcane connection, warm or cool their blood to withstand extreme conditions, or compel a target to perform a single non-suicidal action. They may also thieve life essence after causing a wound, absorbing a quarter of the damage dealt to heal themselves or another.
The pinnacle of blood magic allows for devastating harm to a single victim (2d10) or explosive damage against a group (1d10). An archmage can compel a target to obey for a scene in non-suicidal ways, or for a single potentially suicidal action. By possessing a sample of a victim’s blood the archmage may learn secrets about them, or use it as a continuous arcane connection. An archmage can steal blood from a target and use it to heal for 2d6 worth of physical damage.