Millie Maxwell is a supporting character in the anime film Black Clover: Sword of the Wizard King. She serves as a researcher for the Clover Kingdom's 0th branch of the Magic Tool Research Lab, a division that includes former members of the Eye of the Midnight Sun. Millie has a slender build, with medium-length, wavy green hair that she ties back with a red headband, and green eyes. She was created as an original character for the film and did not appear in the original manga series, though later manga chapters have referenced the film's events, effectively incorporating her into the canon timeline. In the story, Millie is part of the allied forces that arrive to assist Asta and the Magic Knights during the final stages of the conflict against the resurrected Wizard Kings and Conrad Leto. Her background as a magic tool researcher suggests she contributes technical or support-oriented abilities, though specific magic or combat skills are not detailed in the available sources. Her personality and individual motivations are not extensively explored, and she does not undergo a significant character development arc within the film. Her role is primarily defined by her affiliation with the 0th branch and her participation in the larger group effort, without strong individual relationships or standout abilities being highlighted.