A scourge is a flogger that is meant for severe torture of the victim. To achive this, most scourges have metal pieces at the ends. The metal can be formed like metal balls to cause bruises or like fishing hooks or mails to rip pieces out of the victims flesh.
Because of the severe injuries the scourge can create (even the ball versions can cause damage on the spine and organs), the scourge is not a good toy for S&M.