Dark magician girl

A dark Magician Girl is a female practitioner of the dark art found in many fictional mediums and stories, though as the name implies they are antagonists to the band of heroes, this is not always the case and their alignment is actually in line with the protagonists and instead the name alludes to the type or origin of the magic they use being in some way malicious, forbidden or in a sense 'dark' as compared to other magic with more benign uses or origins, thus descriptors of 'light' are in use. The name is also a trope in wikitropes that names and classifies the identifying traits of this archetype character in fiction.
Very popular line of Otaku figurines can also have Dark magician girl used as the defining identifier of the statuette to invoke a certain theme or visual style and attitude from viewers in Japanese statue modelling.