https://wow.gamepedia.com/Gerard_Abernathy#Dialogue_about_Theresa
Gerard Abernathy says: It was simple once I broke her spirit.
Gerard Abernathy says: Everyone has a weakness, it’s just a matter of finding it.
Gerard Abernathy says: I managed to discover that certain parts of the brain when removed or stimulated will make the subject much more docile.
Gerard Abernathy says: You don’t expect me to give up all of my secrets, do you?
Gerard Abernathy says: A little torture, a pinch of magic, and an ample helping of invasive surgery. She was conscious, of course.
Gerard Abernathy says: A little ritual torture can go a long way.