A Mord-Sith is selected at a young age to begin their training. They are trained with an Agiel. Eventually, the girl will "break" and that is when her training is complete. Once completed, they are told to kill their loved ones to prove to their Mistress that they are no longer innocent. After they prove their loyalty, they are to serve Darken Rahl and his successors.
Mord-Sith serve the Lord Rahl by torturing his enemies and turning them into mindless pets. The pets are hung from a chain and tortured, no matter how long it takes until their spirits are fully broken. Most men break in the first training session, when they realize that they will never be free again, and that they will soon be begging to please their Mistress.