The film chronicles the life of Ann Lee, the influential 18th-century Shaker leader revered by her followers as Mother Ann.
On The Red Carpet caught up with the cast at the premiere, where they spoke about the film's unconventional approach.
Seyfried, who stars as Ann Lee, told On The Red Carpet what intrigued her.
"It was the only time I'd ever read a script where I was thoroughly confused as to what this would look like," she said.
"Especially when you have a movie where you're getting to express yourself in other ways besides speaking and relating, dancing and moving, and vocalizing and singing, all that enhances the experience for the actor as well. I became more of myself but also more of Ann Lee."
The film is directed by Mona Fastvold who teamed up with collaborator Brady Corbet, with whom she earned an Academy Award nomination for best screenplay for "The Brutalist."
Lewis Pullman, who plays Ann Lee's brother William, described the film as both immersive and transportive.
"It's as much of an entertaining movie as it is sort of like a weird bath of time travel," he said.
"It is very historically accurate, but the way that it was shot was, as Mona says, like 'crawling into a painting.'"
The film also stars Thomasin McKenzie, Tim Blake Nelson, Stacy Martin and Christopher Abbott.
"The Testament of Ann Lee" premieres Dec. 25 in theaters.
Amanda Seyfried talks about her role in 'The Testament of Ann Lee'
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