The moment the scalpel cut into her skin and drew blood, the spilt life force was converted to raw power which was absorbed by Lucius. The sacrifice of her blood would weaken her but would do no long lasting damage. A night's rest would be enough to reverse the drain of energy.
Lucius watched as the man sliced with a supernatural speed, never once cutting anywhere but on the symbol. He wiped away the blood and continued, this time cutting away a small portion of her flesh as he cut around the area and then cut it away cleanly. The only pleasure that he gained was from the dark power that coursed through his veins. The power was very addictive and he had been taken by it with his very first sacrifice.