Alexander Siddig, known for his roles on such television series as "Game of Thrones" and "Star Trek: Deep Space Nine," will join Fox's "Gotham" later this season as classic Batman foe Ra's Al Ghul.

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The leader of the League of Assassins who's been kept alive for centuries by the restorative properties of the Lazarus Pit, the DC Comics supervillain operated behind the scenes of The CW's "Arrow" before emerging as the primary antagonist of Season Three. Played on that series by Matthew Nable, Ra's was killed by Oliver Queen.

On "Gotham," Ra's will be introduced as Bruce Wayne (David Mazouz) pulls the veil of the Court of Owls to discover the man pulling its strings. Leader of the League of Shadows, the enigmatic and powerful Ra's Al Ghul will quickly prove himself to be Bruce's most dangerous adversary yet. Sidding will appear on the series in a recurring role.

Alexander Siddig on Game of Thrones

Created by Julius Schwartz, Dennis O'Neil and Neal Adams, Ra's Al Ghul debuted in 1971 in "Batman" #232, and went on to become one of the Dark Knight's most enduring rogues. The father of Talia Al Ghul and grandfather to Bruce Wayne's son Damian, aka Robin, Ra's has appeared frequently over the decades, not only in comic books but across animation, video games and live-action film and television. He was notably portrayed by Liam Neeson on the big screen in "Batman Begins" and "The Dark Knight Rises."

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In the comic books, Ra's has a complicated relationship with Batman, whose secret identity he deduced by the time of their first meeting. Although they're mortal enemies, Ra's Al Ghul once considered the Dark Knight as his potential heir because of his relationship with daughter Talia, and continues to admire the vigilante's intellect. Despite long knowing that Batman is secretly Bruce Wayne, Ra's has never made that information public.

A veteran of TV and film, Siddig played Dr. Julian Bashir on "Star Trek: Deep Space Nine" and Prince Doran Martell on "Game of Thrones." His credits also include "24," "Da Vinci's Demons," "Primeval," "Kingdom of Heaven" and "Clash of the Titans."

"Gotham's" third season returns Monday, April 24, at 8 p.m. ET/PT on Fox. Siddig debuts as Ra's Al Ghul sometime later in the season.