Scylla?

Scylla and the other blood users can burn off blood as a component for various magical effects. Scylla specializes in short-term transformations, such as stretching out limbs, popping out crystallized blood for projectiles or body blades, or reflexively hardening body parts for defense. This is all in addition to normal hyper-regeneration and over-active healing factors that force them to actively use their powers or suffer the negative effects of being full of too much blood.