The League of Shadows is a criminal and terrorist organization, focusing on extortion, manipulation and power-broking. One of their most senior members is the Sensei. They also have many assassin operatives, including Cheshire. They are headquartered on Infinity Island, somewhere in the Eastern Caribbean Timezone. They are in league with The Light.
The League of Shadows abducted Dr. Serling Roquette to create for them a weapon from nano-robotics. This weapon, called The Fog, is capable of eating through matter, as well as downloading top-secret plans from computers. After Roquette was rescued by Red Arrow, the League sent Cheshire to kill her in order to prevent her from developing a computer virus that could disable The Fog. Cheshire had succeed in bypassing Roquette's protectors, Young Justice, but too late to prevent Roquette's virus from being uploaded. Under such circumstances, she had been ordered to spare Roquette in case her talents became useful to the League in future. Before being disabled, The Fog successfully transmitted data to the Shadows that it had stolen from Miami Beach University and STAR Labs. They were unable to get data from their next target, Wayne Tech.
Ra's al Ghul
Typical Shadow Operative