Darkness and Poison

Initially, Zero and the other girls wanted just to kill their tormentors. But, after they saw what Zero was doing under Wain's guidance, they changed their minds. Zero tortured the chief scientist in every way possible. The needles were just a warm-up before the real test of fortitude.

Wain was a very experienced man in this business, which any inquisitor would envy. Following his advice, Zero ensured that the scholar did not bleed out, was in incredible pain, and remained conscious. 

It was a balance that only a true devil and a consummate master of torture could achieve.

The final chord was the cutting off of the skin while the scientist was still alive. Even Teresa shuddered at such a gruesome scene. As an assassin for hire, she had often seen people tortured. 

But, Wain was able to impress her. Moreover, Wain himself did not even touch the man. Everything was done by Zero, who was obsessed with hatred for this man.