Mysterious Heroine X

, Class Name , is an Assassin-class Servant Universe Servant summoned by Ritsuka Fujimaru in the Grand Orders of Fate/Grand Order.
==Profile==
===Identity===
Also known as and just X, Mysterious Heroine X is an unknown heroine who tasked herself in eliminating Saber-class heroines during Back Alley Satsuki - Chapter Heroine Sanctuary. Bearing the code name "A-X", X was a stranger who came from the "mysterious dimension" called the Servant Universe. Seeking to accomplish her "true, dearest wish" to "defeat all Sabers", she brandished Secret-Calibur and left her home town, leaving behind an "expression full of bitterness."
Even before arriving at Chaldea, she managed to save an ancient royal dynasty from a crisis, settle the internal strife of the "Mankind Integration Union", and rout invaders from another universe, but such actions were trivial enough for her to not even remember accomplishing them. She will continue to brandish her sword until her goal is completed, and can still be seen "dashing across the sea of stars" even today. No matter what, she also plans to cut down the "Golden Great Emperor Cosmo Gilgamesh."
X has revealed to none that her true identity is actually Artoria Pendragon. While she believes that her "perfect disguise" has tricked everyone, it is asked that others keep the fact quiet to keep from spoiling it and also for the sake of X's own honor.Fate/Grand Order - Mysterious Heroine X Profile, Translated by Master of Chaos.
===Appearance===
X's appearance is said to be of a young woman with "rough and sporty garments unseemly for Servants." Her blue muffler is a symbol of courage, and her cap is used to hide her identity and , although it sticks out of the cap.
===Personality===
Annihilation List.jpg|
Although Assassin displays a "carnage mode" wagering her single holy sword on nothing but defeating all present Sabers.
Mystery Heroine X's wish for the Holy Grail is the destruction of all other sabers. Or at least for them to change their class name to Attacker or Swordsman or something.
====Relationships====
;Nero Claudius
:"You've finally shown yourself, Red! Let's go! Excalibur!"Fate/Grand Order Lines
;Mordred
:"You've finally shown yourself, my delinquent son! Now, here's the punishment for destroying the castle walls!"
;Gaius Julius Caesar
:"I...Impossible! He's...a Saber...with a body like that?"
;Artoria Pendragon Alter (Lancer) / Artoria Pendragon (Lancer)
:"Yes, yes... Even though there are more Sabers, there's more me now, too. However, I just can't let those two sacred lance wielders run amok! No... I mustn't allow it! How'd they grow so much anyway!?"
;Mysterious Heroine X Alter
:"What!? Ecchan is here!? And she's angry about someone organizing her room? I need Japanese sweets, quick! It's the only way to calm her rage! It'll be okay. She's a total sucker for these things."
;Artoria Pendragon Lily
:She opened her heart towards Saber Lily alone.
:"Too soft!" (No self-awareness about her own softness)Fate/Grand Order material III Mysterious Heroine X's Profile, translated by Reddit User ComunCoutinho.
;Saber Class Servants
:"Sabertei Must Be Destroyed."
;Mysterious Sailor X
:"...Huh? Who are you? Someone from Episode II perhaps?"
==Role==
=== Back Alley Satsuki - Chapter Heroine Sanctuary ===
Mysterious Heroine X originally debuted as a joke character in the April Fools visual novel of 2013: Back Alley Satsuki - Chapter Heroine Sanctuary, alongside Satsuki, Sion, Riesbyfe, and Ciel as one of the five “Bronze Heroines.” She and Ciel join the initial trio of Satsuki, Sion and Riesbyfe after their defeat of “Hassan-Ko,” MHX declaring defeating those of the Saber-rank was under her jurisdiction. Specific information unavailable, English translation only provided for Prologue and Chapters One and Two.
She was declared primarily a background character who did little, aside from single-handedly defeating the third Gold Heroine, Nero Claudius.
===Fate/Grand Order===
====Event: SABER WARS====
X crash lands into the Singularity that Ritsuka and Mash are using to help train Artoria Lily when her ship, the Du Stallion II, is sabotaged by Ultra Heroine Z. Emerging from her ship, she criticizes Artoria’s attitude as pathetic and fainthearted. She then fights her to show her what a true Saber is. Though Ritsuka’s party defeats her, X claims the fight was a warm-up and her struggling was her holding back. She introduces herself and decides to take on Artoria as her student, which Artoria accepts. X tells her she needs three kinds of materials possessing mysterious powers spread across the world in order to repair her ship. After Artoria accepts the task, X informs the group they must defend the ship from monsters and collect Artorium particles from them, which she’ll use to power up Artoria.Fate/Grand Order - SABER WARS: The Caliburn Awakens, Episode I: Lily's Departure
After the group defends the ship, X explains Artorium powers her ship and its Spirit Origin Enhancement Device, Adam Kadmon, which will be used to enhance Artoria Lily. Blackbeard then suddenly appears with a rather Gilles de Rais. Blackbeard wants Artoria Lily and Mash as his wives while Gilles wants X's ship parts. The group defeat Blackbeard and tie him up. Despite the protests of the others, Artoria Lily agrees to let Blackbeard train her. Training is cut short, however, after Blackbeard is struck twice in the crotch by Caliburn thanks to Artoria’s lack of aiming.Fate/Grand Order - SABER WARS: The Caliburn Awakens, Episode II: Blackbeard Awakens
The next day, Artoria asks X where she is from. X takes her question as her having an ulterior motive until Artoria explains she wanted to make a popular dish from X’s hometown as thanks for helping her. X reveals she came from the Servant Universe’s future to the present in order to save the future. She then instinctively attacks Nero Claudius when she, EMIYA and Tamamo-no-Mae, arrives to investigate her ship. After her group is defeated, Nero offers to be Artoria’s sparring hero. X protests and tries to fight Nero again, but EMIYA stops her. He offers to train Artoria instead, which both she and X accept.Fate/Grand Order - SABER WARS: The Caliburn Awakens, Episode III: Revival of Rome
After X quickly defeated Paracelsus, Okita Souji, Medea, Medea Lily, and Siegfried when they came for her ship, Artoria questions her actions since they could’ve reached an understanding if they talked. After they defeat Charles Babbage, Sakata Kintoki, and Nikola Tesla, Ritsuka, Mash, and Artoria asks X about her true motives since Babbage warned them about her ship. X explains that the reason the future is doomed is because of an economic crisis in her universe caused by the Saber class’s value plummeting thanks to their overabundance in the future. Now understanding X’s reasons for instinctively attacking any Sabers she sees, Artoria wonders if she should be destroyed as well. But X explains she must allow one Saber to live, otherwise she wouldn’t exist. She believes Artoria to be that one. Suddenly, she is ambushed by Z, paradox version of X to kill her after she fulfilled her mission in the past to kill all Sabers. While she is unconscious, the group defeat Z.Fate/Grand Order - SABER WARS: The Caliburn Awakens, Episode IV: Awakening of the Universe
After she wakes up, X thanks Artoria for saving her. She then admits that she was deceiving her the whole time, but Artoria wishes to continue her training since X believed in her. Taken aback by her innocence and kindness, X postpones her mission to continue Artoria’s training. While Artoria is training, X tells Ritsuka that Artoria cannot change Britain’s fated destruction. Despite that, she feels Artoria can at least change the process. She then tells Ritsuka that she and Artoria owe a lot to Chaldea, and offers to help them.
==== Event: The Garden of Order ====
X crashes into the Ogawa Apartment following a highly concentrated Saber signal. In response, Shiki Ryougi changes into her Saber self. Terrified of her, X claims she had the wrong person and asks to be allowed to go home. But she is forced to fight Shiki when her emergency warp fails. Shiki defeats her, but X claims it doesn't count unless she loses against a blonde Saber. She then retreats after saying they’ll meet again as friends.Fate/Grand Order - The Garden of Sinners/The Garden of Order: 8th Floor, Room No.4
==== Final Singularity: Solomon ====
She is amongst the Servants to assist the Chaldea against Demon Gods Pillar.Fate/Grand Order - Salomon: The Grand Time Temple - Act 09: X / Disposal Chute Andromalius
====Musashi Trial Quest====
X traps Ritsuka and Miyamoto Musashi inside a Reality Marble with her W.F.D. Bracelet when they arrive at third gate. She ambushes Musashi with projectiles, but Musashi deflects them. Showing herself, X declares that a true Saber only holds one beloved sword in hand and that the twin sword style is the ultimate way of evil (ignoring the fact that she does precisely that when using Secret-Calibur). Musashi acknowledges X’s swordsmanship as first-rate, even though it’s from a school she’s unfamiliar with. While X struggles during their duel, Musashi finds her weak point with her Mystic Eye. Musashi then destroys X’s W.F.D. Bracelet to remove the Reality Marble. X is angry that Musashi destroyed it since Lionhead made it. Though she claims Musashi hasn’t won yet, she decides to retreat out of fear. She also tells her to watch out for when a second and third her arrive. She then disappears after saying goodbye to Ritsuka, hoping to see them again.Fate/Grand Order - Musashi Trial Quest: Interlude, Third Gate
==== Mysterious Heroine X (Alter) Trial Quest ====
X is a student at Cosmo-Chaldea High School. She is eating on campus when she meets Mysterious Heroine X Alter. X Alter ask her where she is. X tells her when the school principal, God Bless Edison, appears and scolds X for skipping class to eat. X tells him she's going to give X Alter a tour, assuming she is a transfer student. She then asks for X Alter's name, but the latter can only recall "Ex". Edison informs X Alter that she'll need to meet certain qualifications if she wishes to enroll. X Alter decides she wants to enroll to become a great Servant. Considering her words to be sincere, Edison says she passed the first entrance exam. He then has her and X do a mock battle, and he'll judge her enrollment based on the results.Fate/Grand Order - Mysterious Heroine X (Alter)'s Trial Quest
Later, in her dorm, X accidentally kicks K6-X4 as she complains about how boring Nameless Red's lectures are. She bangs on the voloid when X Alter enters the room. X Alter informs her they'll be roommates starting today to X's dismay. She then sets up territories and removes X's soda from the fridge to stuff her snacks in there. X believes she is taking over her room and readies to fight her again. X Alter then protects K6-X4 from X's attack. They fight until they're interrupted by the Student Dormitory Supervisor who kicks RK6-X4, which somehow results in their voloid body being accidentally cut down by X.
X later leaves to deal with the increasing number of Heroine Zs. Her absence is a sign of relief for Saber students.
==== GUDAGUDA Meiji Restoration ====
X appears under the name of Mysterious Chousokabe Heroine X as one of the Servants summoned by Andras to serve Oda Nobukatsu. She defends the Sun Fortress against Ritsuka’s party while Nobukatsu sacrifices Chacha to Andras. Ritsuka’s party defeats her and Andras’ other Servants.Fate/Grand Order - GUDAGUDA Meiji Restoration, Section 5: The Secret Emiyamaru
==== Summer Event: Dead Heat Summer Race! ====
X appears before Oda Nobunaga as the latter contemplates what to do regarding her driver for Ishtar's race. She shows Nobunaga her space driver's license and galactic certification that she possesses the EX Riding Skill. Nobunaga hires her immediately, feeling she has the ambitions of a true hero. X, elated to find someone who understands her, vows to win the race and to eliminate any Saber on the track or within its vicinity, including those in the stands.
At the racetrack, X vows to eliminate Nero Claudius and Artoria Alter, still seeing them as Sabers even though they're currently Caster and Rider respectively. She also senses the birth of a new Saber and declares someone is going to be taken out the moment the race starts. Ishtar then shows everyone the ritual tools, which are key to erasing the Singularity, and indicates a team is a legit participant. They’re designed to integrate into the vehicles, and any vehicle trying to race without them is automatically disqualified. After commentary on each team from Ishtar, the race begins. Nobunaga and X are the first out of the starting line, but Ishtar shoots them down for breaking the rule on flying.
A group of thugs soon appear before the racers. After the thugs are defeated, their leader, Atalanta, arrives. She considers the thugs to be her children to the racers’ confusion. Calling the wasteland the Atalanta Plains, she tells the racers that its roads lead to where she and her children planted Seed Apples. They are essential to her children‘s future, so she cannot permit them to be destroyed in the race. Everyone ignores her but soon learns she planted land mines to protect the seed apples. Atalanta is eventually defeated, and the racers move on to the next area.
The race brings everyone to an active volcano, where they meet Boudica at its crater. She offers to cook them something, only to turn hostile. Her hostility is due to what happened to Britannia and the fact she doesn’t have a playable swimsuit version this year despite modeling in one last year. She has become an Avenger, believing she must utterly break the racers’ spirits to protect her homeland. She will do so through a game of chicken to the mouth of the volcano, setting it up so the racers can’t cross the volcano until they beat her. The racers accept her challenge. Nobunaga and X end up winning the challenge since they went into the volcano. The ship's reactor overloads and triggers an eruption, shooting the team out into the stratosphere.
Eventually, the racers arrive at a river. Penthesilea appears and explains the more beautiful they are, the faster they will go. She introduces them to the judges: Mister B, who judges their personal beauty, and Leonardo da Vinci, who judges their vehicles’ beauty. X opens the ship's hatch so Nobunaga can show off the bikini beneath her shirt. She warns Nobunaga not to get blown away by the wind pressure but tells her to at least fall onto a Saber if she does.
The racers soon enter the fourth area, which has breast-shaped hills. Artemis and her copies fire upon them, warning they cannot go through Artemis Valley as they please. She will allow them to pass if they can find the real Orion among his copies and return him to her. Nobunaga and X try to bypass Artemis like Nero and Artoria Alter failed to do, but like their predecessors, they're hit by a volley of arrows.
Afterward, the racers reach the final area, a bridge over a large ravine, with the Ishtar Temple at the finish line. However, everyone is sent plummeting when someone cuts down the bridge.
==== Summer Event: Death Jail Summer Escape ====
The racers find themselves at the bottom of the ravine. They’re attacked by the Hessian Lobo security system, which overwhelms them. Medb then arrives and arrests the racers for placing weird textures on her land without permission. The racers fall unconscious and wake up in Medb’s prison. They find out that their powers are negated within prison. Medb tells the racers that she locked their vehicles up somewhere outside the prison after sensing a strange power from them. The racers are then brought to their cells, where they soon meet Ishtar’s avatars. They then encounter Carmilla working as a prison guard. Carmilla determines they're too weak to escape and opens their cells.
In the courtyard, X goes with Nobunaga to speak with the other prisoners, all the while exercising her license to kill on those who refuse to cooperate. They soon learn of a prisoner known as Scorpion who's only brought out of solitary confinement for exercise. This information is relayed to the other racers, and they all learn Gorgon is the prisoner. Gorgon agrees to tell the racers about the prison if they help with her exercise. However, the fight is soon interrupted by Florence Nightingale, who leaves after Gorgon says none of them are injured. Minamoto-no-Raikou deduces Gorgon is a projection of her real self inside her cell. Gorgon confirms this then reveals it's impossible to destroy the prison’s barrier from either the outside or the inside. However, the racers can take advantage of Medb’s overconfidence in her Prison Field to find blind spots to escape. Carmilla then brings the racers back to their cells.
The next day, the racers still haven’t found an escape route. They see Quetzalcoatl training other prisoners to be luchadors After some sparring, the racers are sent back to their cells. They then follow Ritsuka’s advice to dig their way out of the prison.
However, the racers' tunnels all converge onto Gorgon's cell, where she is chained there by divine steel. Gorgon asks the racers to stop Nightingale from spraying her with reptile sanitizer. But the racers remind her that they were never friends and that she only used them to vent her frustrations. Gorgon replies that she'll help them if they defeat Nightingale. After Nightingale is defeated, Nero determines they can use Gorgon’s acid to clear any obstacles that bar them while digging. Since they had a deal, Gorgon spews acid into special containers for each team.
Unfortunately, while digging, they discover the Prison Field extends underground. They return to Gorgon's cell, who seems to be enjoying their predicament. After venting their frustrations, the racers realize they have no choice but to kill Medb to disable the Prison Field. Gorgon reveals there was another prisoner who tried escaping by killing Medb. She defeated them and revealed she has a conceptual weakness to projectile cheese; Nobunaga rolls and laughs on the floor upon hearing this. But Medb is always protected by her warriors. Gorgon reveals Medb always takes a shower in her warden’s office at the same time every day. James Moriarty, Thomas Edison, and Tesla point out they need someone intelligent as them and Babbage, who also knows the prison’s layout if they want to successfully snipe Medb from outside her bathroom window. X smacks Nobunaga down for being dense, and apologizes to Gorgon for her partner's behavior. She promises to keep her in check, calling herself an ace Saber with a high social IQ. But with no race to focus on at the moment, X decides to wait for a chance to catch the new Saber off guard. She stares intensely at Frankenstein. Gorgon reveals there is a prisoner who knows everything about the prison, despite being in solitary confinement. She then gives the racers general directions to that person's cell.
After building it with the materials Ritsuka provided, the racers use the cheese-apult to assassinate Medb while she’s in the shower. However, Medb kicks the cheese away thanks to training her body to automatically react to incoming cheese. As there was nothing Sabery about Medb's kick, X has nothing but praise for it. Enkidu reveals there is another way to remove the Prison Field, one only they know of. They reveal the control device for the Prison Field is a stone above the ground. The racers soon realize it’s in the statue of Medb in the courtyard. Enkidu then reveals there is a prisoner who is master of disguise that the racers can use to trick Quetzalcoatl into disabling the Prison Field. The racers then dig their way to the prisoner’s cell.
They arrive in the prisoner's cell, only to find Carmilla there to their shock. They fight her, but in the midst of it, she turns into Nightingale. After being defeated, she reveals herself to be Yan Qing in disguise. He agrees to disguise himself as Medb to trick Quetzalcoatl into disabling the Prison Field in exchange for fighting him. But Raikou has him sit in the corner and lectures him until he gets sore. Afterward, Yan Qing (disguised as Med) gets Quetzalcoatl to disable the barrier underground, allowing the racers to reach their vehicles in the warehouse.
The racers escape to the outside. X is nearly buried alive, but manages to break free with X-Calibur. Medb and Quetzalcoatl then confront the racers. Medb deflects shots from X's cheese blaster and decides to execute the racers, accusing them of covering Connacht with textures of another place. The racers defeat Medb and Quetzalcoatl, then return to the race once they disappear.
If Nobunaga and X are in the lead, X injects the tank with liquid Artorinitrium that she synthesized while in prison. Nobunaga is impressed but is concerned that they'll explode. After a brief moment of silence, X replies that it will be fine as long as they cross the finish line.
After the race, however, an enormous storm moves toward the track as if it has a will of its own. Ishtar reveals this was her plan. Unbeknownst to the racers, their vehicles’ tires were carving magical energy into the Venus textures she placed on the land. She then reveals her temple to be a giant ATM called the Ishtar Quantum Power System. The racers confront her when the relics she had them install in their vehicle are suddenly removed. The relics converge at the Ishtar QPS, which gathers the magical energy expended in the race. At the same time, the relics were storing the heat created by the friction of the racers’ tires running across the Venus textures for each relic to reach an excited state. The purpose of all this was for Ishtar to create a new Gugalanna. After using the relics and the Ishtar QPS to do so, she declares she can use him to destroy the Singularity. Da Vinci points that would work, but it’d also destroy Connacht. The racers then fight Ishtar and Gugalanna before he’s completely formed, but they struggle against him. Quetzalcoatl then arrives to attack Gugalanna, revealing the her that disappeared before was Yan Qing in disguise. After she destroys Gugalanna, the racers and the race’s administrative staff get their picture taken by Georgios.
If Nobunaga and X won, Nobunaga uses most of their winnings to repair X's ship to its original form after it got wrecked. X is caught in Okita and Chacha's Noble Phantasms when they launch them at Nobunaga for not paying them back.
====GUDAGUDA: Legend of the Imperial Capital Grail====
X appears under the name of Kasuya Heroine X as one of Chacha’s Seven Imperial Spears. She mistakes Okita Alter for a Saber, and though she is corrected, she decides to hunt Okita Alter for her face alone.Fate/Grand Order - GUDAGUDA Strange Tales of the Imperial Holy Grail, We the Imperial Capital Seven Spears She later ends up fighting Okada Izou, who claims to be neither Saber nor Assassin, but a man-slayer. X helps Ritsuka’s party defeat him, angry at an Assassin imitating a Saber. She also tells Okita Alter to meet her at the back of the gym after school, for she has something to say about her face.Fate/Grand Order - GUDAGUDA Strange Tales of the Imperial Holy Grail, Legend of the Mightiest of the Bakumatsu, IZO
====Event: SABER WARS II====
Mysterious Heroine X appears in the SABER WARS II event.Fate/Grand Order - SABER WARS II - To the Beginning of Space, Big Blue Tank IFate/Grand Order - SABER WARS I: To the Beginning of Space, Big Blue Tank IIFate/Grand Order - SABER WARS II: To the Beginning of Space, Sargasso Abyss IIFate/Grand Order - SABER WARS II: To the Beginning of Space, Queen's High School IIFate/Grand Order - SABER WARS II: To the Beginning of Space, Dark MaannaFate/Grand Order - SABER WARS II: To the Beginning of Space, Primitive Red Rose (cont.)Fate/Grand Order - SABER WARS II: To the Beginning of Space, Return of Refugee X
====Interlude====
===== Saber Slayer: Dawn =====
X tells Ritsuka and Mash that there is a tournament for the title of Saber of Sabers. She states she cannot stand that Sabers are gathering from all over the world to participate. She is angry she didn't get an invitation, claiming herself to be the greatest of all Sabers. She says she will not allow a tournament that will not admit her to happen. She decides go in anyway to show the others what a real Saber looks like.
Entering the tournament at the third round, X faces off against Mordred, who quickly recognizes the former as her father. X replies she doesn't know whose child Mordred is, and fights her. After defeating Mordred, X claims Britain's crisis has been averted, and states another Saber who isn't her is gone. Mash wonders if X met Mordred somewhere, but X adamantly denies Mordred being family.
===== Saber Slayer: Clash =====
X has already defeated countless Sabers in the tournament. Her opponent is Nero, and claims she would be getting more cheers if they were in Britain instead of Rome. Nero proposes a pre-battle song, but X interrupts her and claims she came to stop her tyranny. She addresses her as Red Saber, which causes Nero to recognize X's face. X declares she cannot permit red in the Saber lineup since she didn't give her permission. She then fights Nero, and offers to forgive her if she throws her a feast. But Nero refuses, so the fight continues. After she is defeated, Nero finally remembers X's true identity, but X angrily finishes her off when Nero calls her Jeanne d'Arc.
===== Saber Slayer: Awakening =====
X and the others travel to a castle in Britain to face her final opponent: Artoria Pendragon, whose very confused by her participation. X says she and Artoria are two sides of the coin, and claims she cannot become a true Saber unless she defeats her. She then prepares to fight Artoria, even though she is concerned about causing a space-time collapse. Artoria decides to fight X, declaring she cannot her out into the world for her and others' sake. As the fight continues, Artoria asks X what drives her. X answers that Artoria wouldn't understand the terror of seeing many more of her own face appearing; Romani Archaman says she understands though. The two then empower their holy swords, not wanting lose against the other, and continue their battle. Despite Artoria havng the home field advantage, X is able to defeat her. X is then congratulated by the other Sabers for winning the tournament. She is about to "reveal" to Ritsuka that she is in fact Artoria, but the sound of Mash telling her that dinner is ready wakes her up, making her realize that the entire thing was only a dream.
===Other appearances===
She appears as alternate costume of Saber in Fate/EXTELLA.
==Abilities==
X claims to be the "definitive edition of the Saber Class," however, feeling threatened by rise of Red Saber and Dark Saber, she swore to eradicate all Sabers! Going by the logic that she acts as an her Class was set as Assassin. Just like Mysterious Heroine X Alter, Heroine X is known as an agent capable of single-handedly destroying entire planets in the course of their missions. When the two of them worked together, they could limit the collateral damage to a single planet.Fate/Grand Order - Mysterious Heroine X Alter's 1st Interlude: XXXX. Mysterious Heroines
===Combat===
Mysterious Heroine X fights using a style called Saber Ninja Arts. It is an extraordinarily powerful cursed technique, but becomes almost useless once its user joins your side. It is a barbaric technique that can only be used alone. It includes techniques that can create afterimages with Saint Graphs.
Mysterious Heroine X is usually protected by the rules of the Cosmos Dimension (comedy characters can't die). However, characters such as Shiki Ryougi, whose manner is serious and menacing, can ignore this rule, making X fear for her life and try to escape when meeting them. Shiki defeated her before she could do so, although X claims that as long as she isn't a blonde Saber it doesn't count. Despite being a master swordsman, Mysterious Heroine X worries when she senses the same aura from Miyamoto Musashi as she did from Shiki. Just like MHX, Musashi will do whatever it takes to win. Musashi uses her Niten Ichiryu after having set her eyes on X's weakness and targets her left hand. X is unable to stop her, and thus, Musashi successfully destroys her W.F.D. bracelet on her wrist, which had been specially made by the new engineer that joined the Knights of the Round Table team, Lionhead. X runs away in fear.
Artoria Pendragon Lily and Mash Kyrielight were also powerful enough to defeat Mysterious Heroine X. The two of them managed to get in some pretty good blows, making X blurt out some "oofs". When Artoria's hand slipped and accidentally hit her in the skin, X kept saying "It doesn't hurt at all" despite tears welling up in her eyes. An indicator that just like any other Artoria Pendragon, X hates losing. X, however, claims that she was holding back, as she didn't ambush them from the dark, bury land mines, or kidnap anyone important to them. Their match was a fair and square fight, very much like the Saber Class. Mysterious Heroine X, Lily, and Mash fight Nero Claudius, Tamamo-no-Mae, and EMIYA. Although X states they won, Nero says they merely pulled their punches when they realized their opponents were Mash and Ritsuka Fujimaru.
Heroine X states that because Mysterious Heroine X Alter closely resembles her, she did poorly against X Alter in her mock battle. Afterall, she was holding back, wehereas X Alter was really going all-out. X Alter regards X's sword moves as "weak beams." In their next scuffle, X says that although Alter is a nerd, her swordsmanship is spot-on, and that she actually senses that she has had some formal training. As all Saberfaces are Sabers in X's eyes, whether they be Assassin or Berserker, she finally gets serious against Alter. Their fight is interrupted by the Girls's Dorm Supervisor. The reports from their fights reached other members of the Villain Alliance making them believe Alter had great fighting potential. They decided to intervene with a large-scale attack, a Death Tour with enough power to destroy an entire planet. Even X could not save the servant school from that.
When X Alter and Heroine X travel to the Artifical Planet Esaba to rescue a Base Occupied by the League of Villains, X eventually starts coughing blood. She says it's nothing and that she just suffered a flesh wound. She says it'll take more than just a little battle to the death against Savage Queen and a brawl with the squid legions of Tentacle General Sanity Gilles to take her down. The wound had been caused by Herc The Supehuman's baryon ax which had been deflected by Nameless Red, causing it to pierce straight through her side. Had it not been for her afterimages, Heroine X would have almost certainly died instantly. Her condition started getting worse later on due to the wound caused by the Queen’s heavy spear causing an Anti-Healing curse.
During the SABER WARS II incident, Mysterious Heroine X teams up with Space Ishtar and Calamity Jane to fight the Space Shinkageryu. Altera of the Shooting Star claims that when they work together, their "bravery" rivals their own. When they fought Ashtart, she was able to defeat both Jane and X with a single blow. Space Ishtar was the only one still standing after her initial attack. When the team faces Sigurd the Dragon-slayer Sword, Sigurd reveals the secrets about Ishtar's past. Although Ishtar was still shaken up by said revelations, Sigurd doesn't give her any time to recover, and immediately attacks them. Something that isn't honorable according to Ishtar. In this state, their swordplay is no match for Sigurd's and he defeats all three of them. When Mysterious Heroine X fights Sigurd on her own, due to being a genuine dragonkin, she was capable of defeating him. After Sigurd has already gone down, X starts coughing blood, and says she wasn't as good as she hoped about dodging his attacks. He struck with such skill she didn't even realize he had destroyed her Spiritual Core.
===Skills===
====Class Skills====
*Cosmo Reactor (A Rank): A reactor that’s cosmic, it’s allowed only to the shining Saber. The reactor reacts to many things. Like the plot, for example.
*Riding (EX Rank): Talent for riding. She can’t manage most mounts and vehicles, but she is amazingly effective when it comes to piloting junk spaceships. To the point that she can make a ship with no warp function warp. Her spaceship is called . It allows her to go on a journey through space, something that is only possible thanks to the ship being able to travel faster than the speed of light. X is pretty sure that the ship can make time jumps, aka working like a time machine, as it warps after all. It also possesses the following functions:
:* - 
*Presence Concealment (— Rank): Are you implying Sabers have that!? (It’s actually ranked EX, but it’s sealed since she completely denies it).{This skill could be associated with 2 treasures that his Arthur Pendragon template carried; Goswhit(helmet=cap) and Gwenn(mantle=jacket) that had invisibility capabilities that varied in addition to their Carnwennan(dagger)}
====Personal Skills====
*Supporting Bombardment (EX Rank): Using a mysterious communication device, she can have Du Stallion II automatically perform back-up fire. In a duel between knights, there’s no such thing as dirty tricks and underhanded tactics.
:*Supporting Bombardment XEX (EX Rank): Upgrade from Supporting Bombardment. 
*Instinct (C+ Rank): Considerably downgraded compared to the normal Artoria, but it ranks itself up to A-Rank Instinct for anti-Saber purposes only.
:*Star of Saber (C++ Rank): Upgrade from Instinct.
*Galactic Meteor Sword (C Rank): A power given to the Saber that can destroy even stars. Also known as the sword that absolutely kills Sabers. Since it’s super-effective against Sabers, wouldn’t you agree that this makes her the greatest Saber of all?
:*Galactic Meteor Sword XEX (A→EX Rank (Upgrade)): Upgrade from Galactic Meteor Sword. Acts as her second Noble Phantasm.
===Noble Phantasms===
Her Noble Phantasm is Secret-Calibur. This is the legendary Holy Sword, whose last wielder was lost in the last great war. It is the only weapon in the Servant Universe which can destroy the Dragon's Heart jewel at Dark Maanna's core. Although X had always been confident she would be able to destroy the Dragon's Heart she didn't know if she could destroy the ship completely, due to being a relic from an ancient civilization. X also used it to defeat both Okita Souji and Paracelsus von Hohenheim simultaneously. It was also powerful enough to kill Siegfried, Medea, and Medea Lily with a single blast.
X's second Noble Phantasm is Galactic Meteor Sword XEX. Since X would never be able to defeat the Ashtart Origin, Mysterious Heroine X Alter decided to train her. Thanks to X Alter using her EX rank ∞ Chestnut Paste, X was able to awaken a new killer move. This is a move that can only be mastered by a one-of-a-kind heroine by piling enhancements atop enhancements. Something much easier said than done. Eventually, X awakened her true strength, a skill that is truly singular. An EX-ranked skill that surpasses other EX-ranked skills. Alter calls it XEX. After Ishtar Ashtart defeated Ashtart Origin, X used this attack to destroy the remaining shrine Bel Maanna with a single strike. It would have crushed to death Space Ishtar and Calamity Jane otherwise.
==Forms and Alternate Versions==
===Ultra Heroine Z===
 is an alternate version of Mysterious Heroine X who acts as the antagonist of the "Saber Wars" event. An alternate version of Mysterious Heroine X, created by her events in the past, causing a paradox to kill her after she fulfilled her mission to kill all Sabers and thus, become the most powerful Saber in the past. Ultra Heroine Z is mostly the same as Mysterious Heroine X, but she loathes all Sabers (including Lily and especially Nero) and deems MHX a failure as a Saber Killer for "opening herself to the enemy".
By reciting the incantation , she is able to use to duplicate herself into hundreds of shadow clones, though they are noted to not be actual independent individuals and are weaker than the real Ultra Heroine Z.
==Development==
===Creation and Conception===
She makes her first appearance in 2013 April Fools.
Nasu Kinoko is the scenario writer for Mysterious Heroine X in Fate/Grand Order. Takashi Takeuchi is the character designer for Mysterious Heroine X. 
Mysterious Heroine X was illustrated by BUNBUN in Fate/Grand Order.Fate/Grand Order material III - Mysterious Heroine X's Profile translated by ComunCoutinho
==References==
it:Misteriosa Eroina X (Assassin)
Category:Characters in Fate/Grand Order (Part 1)
Category:Assassin-class Servants
Category:Servants
Category:Parody characters
Category:April Fools' Day
Category:Saberface
Category:Servant Universe Servants
Category:Heroic Spirits
Category:Chaotic Good Servants
Category:Star Attribute Servants
Category:Dragon lineage
Category:Servant Universe Inhabitants
Category:B rank Strength Servants
Category:B rank Mana Servants
Category:C rank Endurance Servants
Category:D rank Luck Servants
Category:A+ rank Agility Servants
Category:A++ rank Noble Phantasm Servants
Category:Sovereigns
Category:Introduced in 2013
Category:Voice - Ayako Kawasumi
Category:Artoria variations