Maisie Williams will give the Twelfth Doctor a run for his money on Doctor Who.

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The Game of Thrones star will drop into the TARDIS during season 9, but Williams might not be on the Time Lord's side. Billed as a character that will give the Doctor "exactly the right sort of hell," the young actress could shake up the status quo.

"Whether she is good or bad is up for discussion, I think. She does put the Doctor to the test and it's sort of a dynamic that we haven't seen before," Williams said on The Chatty Man, according to Digital Spy. "There's been a lot of speculation about whether she's like a younger Clara or whether she is a new character completely. I'm not going to tell you which one."

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Willaims is slated to appear in an upcoming two-parter penned by Jamie Mathieson, Steven Moffat, and Catherine Tregenna. It is currently unknown when in the season "The Girl Who Died" and "The Woman Who Lived" will air.

Find out more when Doctor Who returns to the BBC and BBC America this fall. Click the video below to see Williams in season 5 of Game of Thrones.

Tags: Doctor Who television BBC BBC America