The 64-year-old actress is joining returning cast members Sam Worthington, Zoe Saldana and Sigourney Weaver, according to The Hollywood Reporter.
The plot details for the sequels are being kept under wraps.
'Avatar 2' will arrive in theatres on December 18, 2020 with subsequent movies coming out in December 2021, 2024 and 2025.
"Game of Thrones" star Oona Chaplin is one of the few newcomers joining the four follow-ups.
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