Negan may have been defeated at the close of Season 8 of The Walking Dead, but that doesn't mean Rick Grimes and his merry band of survivors are out of the woods yet. Just as one threat is taken care of, another will come to take its place: Season 9 of the series is set to introduce another big villain from the comics in the form of Alpha, the leader of a group called the Whisperers.

During this Friday's The Walking Dead panel at Comic-Con International in San Diego, it was announced that Academy Award nominated actress Samantha Morton has been cast as the villainous Alpha. What we don't know however, is when exactly the British actress, who can be seen in Warner Bros.' Fantastic Beasts and Where to Find Them, will debut on the series.

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Alpha was an important antagonist in The Walking Dead comic books. In fact, following Negan, she was the biggest threat to Rick and his allies starting in the long-running series' Volume 22, "A New Beginning."

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The Walking Dead stars Andrew Lincoln (for now) as Rick Grimes, Norman Reedus as Daryl Dixon, Lauren Cohan (also for now) as Maggie Rhee, Danai Gurira as Michonne, Melissa McBride as Carol Peletier, Lennie James as Morgan Jones, Alanna Masterson as Tara Chambler, Josh McDermitt as Eugene Porter, Christian Serratos as Rosita Espinosa, and Jeffrey Dean Morgan as Negan. The series will return for Season 9 on AMC this October.