Ciel has dark skin, short, navy blue hair and blue eyes. She also has a gold marking consisting of an oval shape surrounded by four smaller circles in the center of her forehead.
She wore a blue beret, a plain off white golden button-down shirt with an asymmetrical collar, a blue combat skirt with black waistband and fingerless, elbow-length black gloves with a wristwatch on her left hand and black shoes alongside white, golden buttoned boot chaps.
She appeared to be very regimented and by-the-book and spoke with a near-monotone, matter-of-fact voice. When Ruby Rose asked if Penny considered Ciel to be her friend, Penny replied that Ciel was merely ordered to spend time with her. Ciel is often seen to be conscious of the time, looking at her wristwatch and literally timing a minute when Penny asked for a minute to herself.
- Her name is French, with ciel meaning "sky", and soleil meaning "sun". Her name fits the Color Naming Rule by alluding both to the blue color of the sky as well as the yellow color of the sun.
- Although her first significant appearance was in "Never Miss a Beat", she cameoed in a photo alongside Penny as Cinder Fall is pre-assigning the contestants of the next day's battle in "It's Brawl in the Family".