Ra's al Ghul is an international terrorist and assassin whose ultimate goal is a world in perfect environmental balance. He believes that the best way to achieve this balance is to eliminate most of humanity. He runs the League of Asassins, an organization of highly trained killers. He is also Damian's grandfather.
After Tim Drake dismantled the League of Asassins, Ra's Al Ghul decided to take his revenge by murdering everyone Tim and Bruce Wayne had ever loved. He politely informed Tim of this plan before he put it into action, so Tim raced out and reluctantly allied himself with Stephanie, the only person he could find.
The first person Ra's targeted was Dr. Leslie Thompkins. After shutting off all communication in Gotham, Ra's sent the assassins after Leslie's files. However, Tim foiled the attempt. Ra's promptly sent the assassins to target Leslie personally at the ball she was attending. Stephanie and Tim arrived to hide Leslie and handily beat off all the assassins.
Ra's was informed that Tim Drake and Stephanie Brown had foiled his plans. He sent the assassin Prudence to kill Stephanie, but unknown to him, she had defected to Tim's side. At any rate, Steph beat her to a pulp.
He also planted a bomb at Tim's base. Tim, Steph and Prudence escaped thanks to a safety measure/booby trap Tim had installed. But Ra's had a backup plan- the trio was confronted by a cadre of assassins as soon as they escaped!
However, Steph not only saved the crew and allowed them to escape, she saved one of Ra's targets, Vicki Vale from being killed, thouroughly foiling Ra's plans.
Find out more about Ra's here.