Kagami

Kagami (鏡, Mirror) is a Demon, more accurately, an Etherious who has been wandering Earth Land for centuries, and gaining the moniker of Lady in the Mirror (鏡の中に女, Kagami no Naka ni Onna), and becoming more of a legend, rather than an infamy as a Demon, due to her Curse allowing her to remain undetected and difficult to find or capture.

Curse
Mirror, Mirror (ミラーミラー, Mirāmirā):

Trivia

 * Kagami's abilities and concept is heavily inspired from the character Bloody Mary, from the game The Wolf Among Us.
 * Her Curse's name is also a reference to the famous line, "Mirror, mirror on the wall", originating from the Snow White fairy tale.
 * Credit goes to User:Perchan for suggesting the name.
 * Her appearance is based off of Calamity from the game Valkyrie Crusade.