Millis Steel is Argus Steel's daughter and the member of the thieves. She, her Father along with Marilyn Flame and Ninja Riot are tracking Diancie to capture her and awaken Diancie's power. During Yveltal's rampage her Chesnaught turned into stone by Oblivion Wing. She, her Father and Argus' Aegislash use their airship to take down Yveltal with missiles but Yveltal avoid them and flies over and grabs the airship and fire his Oblivion Wing turning her, along with her father and his Aegislash in their airship we're turned into stone and crash into the lake. Later she, her father and her Chesnaught we're revive by Xerneas after the crisis is over. In the credits of the film she and her father open up their own chocolate shop together.
- She will become Emerl and his friends' enemy in Team Robot in Pokemon: Diancie & The Cocoon of Destruction.