Nazo no Heroine X is a mysterious Saber-class Servant from Fate/Grand Order, presented as a parody-like, self-appointed “space police” heroine who relentlessly hunts down Sabers. She is portrayed as a secretive, overly serious, and somewhat comedic figure whose identity is deliberately concealed by her name. In the series, she serves as a recurring support character and comic foil, often appearing in events and spin-offs with a blend of seriousness, absurdity, and fan-service appeal.