Fremy has the appearance of a frail girl with white skin and white hair, an eye patch covering her right eye, a leather cape as well as leather clothes, and a black cloth covering her forehead. Her left eye is almost transparent blue and her glare is cold and distrustful. Her eye patch is there to hide the unnatural color of her right eye, and the cloth hides the scar left by the broken horn on her forehead.

Fremy is the Saint of "Powder." Her unique heredity allowed her to receive from the god a type of power that no one ever received before her, as "Powder" isn't among the 78 officially known types of Saints. As such, she's also the only Saint who isn't under the supervision of Mora. Her power allows her to freely create explosives during battles, and greatly increases the damage caused by her gun's bullets. In Rokka no Yuusha's world, guns aren't powerful enough to injure a kyouma, but in Fremy's case, she can easily kill most of the kyouma as well as most armored humans in one single shot. But because her gun need to be reloaded after every fired shot, she's weak in close combat as well as when she's surrounded.