The League Of Assassins was established by Ra's Al Ghul, who is one of Batman's most long-standing enemies alongside The Joker. A believer in world peace, Al Ghul believes that the best way to achieve this is through the destruction of humanity. So, basically, he's a fairly typical megalomaniacal supervillain type. He set up The League in order to protect himself from Batman while he focused primarily on his greater goal, and key assassins such as Lady Shiva, Bane, Doctor Moon, Merlyn and David Cain have all worked for him in this period. In fact, each killer that has joined The League has sworn their allegiance to Al Ghul, displaying a willingness to die for their powerful and spiritual leader. Al Ghul's most famous disciple is undoubtedly his daughter Talia, whose beauty captivates Bruce Wayne on many occasions (and has frequently weakened him in his fight against her father). Talia is also incredibly powerful, and Ra's has frequently longed for a marital union between his heir and his vigilante rival Batman. Trained in the same martial arts that set her father apart as a great warrior, Talia is more than a match for most of the other members of The League. Their prominence in Batman's storyline, as well as their success in bringing together several of the most important assassins in DC's history, makes the Al Ghuls two of the most important assassins in the world of comics.