Mysterious Heroine X Alter is an Assassin-class Servant in Fate/Grand Order, representing an alternate version of Mysterious Heroine X. She is characterized by her obsessive pursuit of Sabers, viewing them as targets for elimination. Her personality is notably eccentric and comedic, often breaking the fourth wall and displaying unusual behavior compared to other Servants. She possesses a space-themed aesthetic and weaponry. As an Alter version, she represents a darker or twisted interpretation of the original character, though specific details about her backstory and exact nature remain mysterious within the Fate narrative.