'Gotham' Ra's al Ghul Alexander Siddig | Hollywood Reporter

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The supervillain will first appear later this season, as Bruce Wayne (David Mazouz) pulls the veil off the mysterious Court of Owls organization and discovers that the man pulling the strings is the enigmatic and powerful Ra's al Ghul. With his past shrouded in mystery, Ra's uses cunning and deception to lay waste to his foes. As the leader of an international criminal organization known as the League of Shadows, Ra's will prove himself to be Bruce's most dangerous adversary yet.

He's most well known as Doctor Bashir on Star Trek Deep Space Nine, but he was also in Game of Thrones. Solid actor and he will fill the role very well, not the least of which reasons being that he matches Ra's ethnicity more accurately.