Everything

By offering up a sacrifice, you also take on the energy of that sacrifice. An offering of love conveys loving Resonance; a terrified sacrifice yields violated Resonance. As the section that deals with Prime Magick and Resonance explains, the energy of an Effect that employs the Prime Sphere gets especially potent Resonance. And so, for reasons that should be clear, messy

sacrifices have messy energy that “sticks” to a person long after the blood itself has been washed away. This “Lady Macbeth effect” taints mages who employ living sacrifices; even folks who can’t normally perceive Quintessence notice something “wrong” about people who steal life-force from other beings.

In addition to the metaphysical effects of unwilling sacrifices, such offerings tend to have physical consequences too. Corpses smell bad, and disposing of remains (especially those from large sacrifices) gets really problematic. Cops take interest when folks start disappearing, especially if corpses turn up bearing marks of sacrifice. Angry neighbors and vengeful loved ones, persistent ghosts, malignant spirits… live offerings bring notorious repercussions, and so despite the traditional practices involved with such sacrifices, such “gifts” are never taken without cost.