I will try my hand at making a Blood Magic with jives with the standard mental track spellcasting as well.
The idea here is to make Blood Magic useful but dangerous as hell.
Blood Magic [-0]
Description: You give your lifeblood as a sacrifice to fuel your magic.
Musts: You must have thaumaturgy, evocation, sponsored magic, or some other form of magical ability.
Skills Affected: Conviction
Effects:
Power in the Blood. You may take physical stress (or physical consequences) in place of mental stress (or mental consequences) in order to fuel your magic. Stress and consequences you take in this way are considered to bypass all catches and thus you do not benefit from Recovery powers, Toughness powers, or Armor.
Backlash of Power. Blood magic is very potent, very dangerous and very addictive. After using blood magic you must roll discipline (with the same bonuses) versus your original discipline roll, as if you were facing an attack of the same value. If the attack succeeds you take an extra toll in physical or mental stress. This extra stress is considered to bypass all catches and thus you do not benefit from Recovery powers, Toughness powers, or Armor.
For Example: Tommy uses blood magic to cast a 5 shift evocation spell. He rolls a 5 to control the shifts of power he called up. Now he must defend versus an attack with an accuracy of 5 and a weapon rating of 0. He rolls a 4 and takes one extra stress, which his player may allocate to either the physical stress track or the mental stress track as he sees fit. If it was allocated to the mental stress track, the pleasure of the power coursing through his body has impacted him in a negative manner. If it was allocated to the physical stress track his body had difficulty handling the strain of so much energy rushing out of him, fatiguing him just a little more than he had expected.