Ra's al Ghul

Ra's al Ghul (رأس الغول) is the leader of the League of Assassins. He is also the father of Nyssa al Ghul.

Biography
Ra's sent a messenger to Sara Lance, ordering her return, though she refused and killed the messenger when he refused to report to Ra's that he had not found her, as she wanted.

About a week later, he sent Al-Owal and a team of Assassins to bring Sara back by force, only to lose his team to both Sara and Oliver Queen.

Moira later contacted Ra's after Malcolm mentioned that he went to Nanda Parbat. It was revealed that Ra's wants to kill Malcolm.

Trivia

 * Ra's al Ghul, along with his daughter, Talia, are normally portrayed as enemies of Batman and his associates. However, his organization, the League of Assassins have a history with Green Arrow and Black Canary.
 * In addition to Ra's being mentioned, Al-Owal also mentioned "the child of Ra's al Ghul" meaning that he was referring to one of his daughters Nyssa al Ghul (Raatko) or Talia al Ghul during the episode League of Assassins.