(n.) the power to manipulate blood like water. It is a variant of body manipulation.
It can be applied in many ways - attacks, clotting, consumption, generation. It is considered to be one of the most sinister abilities, and is often associated with dark magic and voodoo. Those with this ability can shape, create, solidify and animate vellum, whether it be from oneself, others or free flowing. They are also very good puppet masters, creating marionettes out of the strongest of men. They can save or slay you depending on how they are feeling.
Their beating hearts never rest, as they must constantly train to avoid becoming a threat to society. Donating their bodies to science is a popular method to do so. But no matter how hard they try, that might not be enough.