Negga was first cast as a guest star in October 2013, with executive producer Jeffrey Bell later explaining that "Ruth Negga showed up and we just fell in love with her and found ways to use her beyond our initial conception". Negga had originally auditioned to play Simmons, and when the part of Raina came about, the producers knew Negga would be perfect for the role. Foley was informed of Raina ahead of time, allowing her to flesh out the character with illustrations, as well as print specific fabric. When Raina is introduced in "Girl in the Flower Dress", Foley and Negga "wanted to show a progression in her dresses that reflects where her character might be going", with her initially unclear intentions paired with "a softer silhouette" and a pattern of white with black flowers. For her second appearance in the episode, "it's becoming clear that she has an agenda" so the dress is more streamlined, and the colors are flipped to black with white flowers. For her final appearance in the episode, her dress is red with black flowers. Foley concluded, "By the time you see her again in ["The Bridge"] you know she means business". For her appearance in "The Bridge", Foley added leather to her dress to give it "more of an edge". Each dress is custom-made from specific fabric and has a different silhouette. Foley also worked with Tancharoen to match the color of the dresses to the episode's themes. After Raina is transformed in the second season she hides her hideous appearance with a hooded jacket, which Foley subtly added a flower pattern to, as "she was always going to be the girl in the flower dress, so I wanted to pay tribute to that".
