James Spader cast as villain Ultron in Marvel's "Avengers: Age of Ultron" James Spader, left, has been cast as the titular villain in "Avengers: Age of Ultron." Frederick M. Brown / Getty Images; Marvel James Spader will play the titular villain Ultron in "Avengers: Age of Ultron," Joss Whedon's upcoming sequel to 2012′s "The Avengers," Marvel announced Thursday. The film is set for release May 1, 2015. Spader joins the "Avengers" franchise as a respected, Emmy-winning actor ("The Practice, "Boston Legal") with an extensive filmography that includes projects directed by the likes of Steven Spielberg, David Cronenberg and Steven Soderbergh, among others. He's returning to television next month as the star of a new NBC series "The Blacklist," playing an international criminal. Whedon is to film his highly anticipated sequel to "The Avengers" at Britain's venerable Pinewood-Shepperton facility, the same soundstages that played host to Marvel's upcoming "Thor: The Dark World," set for release later this year. PHOTOS: Marvel's Comic-Con announcements It's unclear how closely the film will tie to the recently finished "Age of Ultron" story in Marvel Comics, or whether Ant-Man (the protagonist in another upcoming Marvel film, directed by Edgar Wright) will be part of the film. In the comics, Ultron is an insane, sentient robot who tries to destroy his creator, Dr. Henry Pym, the original Ant-Man. Samuel L. Jackson is "master manipulator" Nick Fury "Avengers": Cobie Smulders up for sequel duty