Carrie Coon has been cast as Proxima Midnight in 'Avengers: Infinity War'.

The 37-year-old actress - who is best known for starring as Nora Durst in the HBO drama series 'The Leftovers' - is to play the part of Proxima, a member of the Black Order, in the much-anticipated new Marvel film.

Carrie - who is currently pregnant with her first child - announced on Twitter: ''It's true! My voice and a dazzle of gifted animators have teamed up to play Proxima Midnight.''

Other actors set to play members of the Black Order include 'Kong: Skull Island' star Terry Notary and Tom Vaughan-Lawlor.

The last-minute casting announcement comes shortly after Elizabeth Olsen - who plays the role of Scarlet Witch in the Marvel movies - revealed that the cast of 'Avengers: Infinity War' still don't know the title to its sequel.

The 29-year-old actress admitted that despite being a veteran of the franchise, she's not been told the name of the sequel, which was shot immediately after 'Infinity War' last year.

Asked whether she knew the title of the follow up, Elizabeth confessed: ''No. Someone just told us that they were going to release it after this movie.

''When are they releasing the name? I have no idea what it is. I've been calling it 'Avengers 4'.''

Elizabeth also revealed she's been sworn to secrecy regarding the film's plot.

She said: ''We can choose to sit in a locked private room with an iPad that has the full script - which also has a bunch of lies in it - because they won't print the full script.

''But if you don't want to do that, they give you your pages that pertain to your character, and then they orally explain to you what's happening in the rest of the movie.

''So we do know what happens as much as they have given us ... unless they're lying to us, and planting strange seeds.''