Feared in many places and dangerous in some, blood magic carries a stigma that's only partially deserved. Simply put, magic users may use blood as a material component for spells, at a rate of 1 hp for 1 gp of value. Powerful wizards and clerics can use their own lifeforce to power potent spells, and a party of adventurers could spill enough blood to raise a fallen ally. However, blood taken by force is all too often used, and tales of sacrifices employed for powerful spells dominate discussion of this tradition. Nextitehuacan in particular is infamous for this, as clerics cast potent magics for their city, and when the Abyss or its agents are near, blood magic can result in Taint, a manifestation of aberrant sickness bleeding into the world.
Blood magic may be the first magic ever employed, and ties in with sacrifices made to the gods. Most civilizations ban it at some point, though not all.
Bloodletting tends to be rapid and violent, particularly for spells cast as a single action. During religious uses, the blood is not consumed, but altered; it no longer provides sustenance for anyone attempting to drink it, as the essence of it has been granted to the gods.
Components and tools
Ritual knives are common in areas where blood magic is practiced regularly and with state consent.