Rose Byrne will be reprising her role as Moira MacTaggert in 'X-Men: Apocalypse'.
Byrne joins a group of newcomers who will play the younger versions of Jean Grey, Cyclops and Storm.
"She's a significant character in the movie," Simon Kinberg, 'X-Men: Apocalypse' screenwriter, told EW.
"We ended 'First Class' with Charles having wiped portions of her memory of her experience with the X-Men. They are, essentially, strangers to her when she meets them."
Byrne's CIA agent was first introduced in 'X-Men: First Class' as the love interest of James McAvoy's Professor X Kinberg said their relationship will be "mined more" in this instalment.
Jennifer Lawrence, Michael Fassbender and Nicholas Hoult will also return, while Oscar Isaac will enter the franchise as the titular comicbook villain.
However, Patrick Stewart has confirmed that he and fellow first generation mutant Ian McKellenwon't appear in the upcoming film as it's set in the 1980s and explores the earlier lives of the characters.
Kinberg also said that 'Apocalypse' will wrap up certain 'First Class' character arcs.
"This movie is the completion of the first arcs of Charles, Eric, Raven, and Hank, who are essentially our main characters," he said. "They're such young actors and young characters, so there's a lot more story to tell. But as a first phase of their lives, there is this feeling of closure by the end of the movie."