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Caster is a magus from the Age of Gods that far surpasses modern magi.[6] She is something from the divine era that shouldn't exist in the Age of Man, so her abilities in magecraft are on an entirely different level than any living magus can produce. While something "solid" like completed spells cannot normally be overcome by a "liquid" such as magical energy, Caster compares modern magecraft to mud buildings that, while solid, can easily be washed away by the violent water current of her superior spells. Even though she is considered a witch, the magecraft she utilizes during the Holy Grail War is forbidden magic she has never before used in her life. Without a proper Master to provide her with magical energy and being the weakest of the Servants, she feels she must abuse such abilities to match her opponents.

She has a large amount of magical energy at her disposal, and at normal levels, she is capable of staying in the world for up to two days without an active contract with a Master even though she lacks the Independent Action skill of the Archer class. Due to her first Master being overly cautious of her abilities, he constantly kept her magical energy level below his own, so she was only able to last a brief period of time after killing him. She normally would have disappeared before finding another anchor to the world, but the Ryuudouji Temple kept her stable long enough to establish a contract with Kuzuki.

She does not need to cast her magecraft like modern magi, as incantations are unnecessary to connect herself with the world. She is always surrounded by divine mysteries of ancient lore, so magic is just something she commands like ordering her guard dog to attack. This stems from her High-Speed Divine Words (高速神言, Kōsoku Shingon?), which allows for the activation of magecraft without connecting to Magic Circuits or using the normal incantations for the spells. Divine Words (神言, Shingon?) are a Thaumaturgical Theory and language from the Age of Gods that modern humans can no longer pronounce.[7] They are fundamentally different from modern incantations due to words themselves having power during that era, while modern incantations are mainly just a means of self-hypnosis to work one's circuits. Caster's use is advanced enough that spells are activated with just a single action, allowing for High Thaumaturgy in an instant.

Castermagecraft

Caster's magecraft

Her main offensive spell is Rain of Light (光弾雨, Kōdan'u?): Machia Hecatia Graea, which is a volley of rapidly fired beams of light each with an A rank power of attack. Each beam is a deadly spell on the level of High Thaumaturgy with three times Shirou's entire amount of magical energy, capable of destroying the body of a Servant with a direct hit. Just the use of one single beam would normally require a magic circle, ten count aria, and one minute of casting for a normal magus, and still thirty seconds with a High-Speed Aria. Caster's Divine Words allow her to shoot them in rapid succession without any preparation after simply targeting the enemy with her wand. She can fire them without pause when she has a supply of stored magical energy, and the result is something that resembles a bombing raid that leaves the ground scorching red.

The speed of Caster's spells cannot be exceeded by anyone because she can bring forth divine mysteries from a single word. Rin Tohsaka, someone who will eventually be among the top one hundred modern magi, is able to match her on a single spell basis by releasing magic directly from her jewels. Equal in speed, it is a battle of power without a "first move" that will end only when one runs out of energy. Caster's spells are strong enough that the only way Rin is able to nullify a single one is by utilizing years worth of magical energy. Even that level of magecraft is simple to Caster, as three full powered jewels from Rin capable of destroying Caster's temple and the entire Fuyuki church are easily nullified after the magical energy is sucked into Caster's robe.

She also uses Αερο (Aero) ( 病風アエロー ,  ShippūAerō ?), which is a plague wind spell that easily minces part of Shirou's chest as if it were sent through an enormous fan. She also makes use of an electrical attack and Κεραινο (Celaeno) ( 疾風ケライノー ,  ShippūKerainō ?).

She also has various support spells like Ατλας (Atlas) ( 圧迫アトラス ,  AppakuAtorasu ?), which freezes the target in place by altering the pressure of the atmosphere to anchor a region of space. Everything in the surrounding is frozen, and it is potent enough to hold even Servants in place. She is able to easily cast it even while using Rain of Light, allowing her to freeze the target before destroying them. Archer and Saber are able to break free by surging their magical energy.

She has a constant protection over her, and she can further shield herself with Μαρδοξ (Argos) ( 盾アルゴス ,  TateArugosu ?), a protective spell that borrows the concept of the Argos. It is a glass-like barrier that has the same toughness as Berserker's skin. Just one of Gilgamesh's swords is able to shatter it like glass. She has a great amount of natural healing like Saber, which keeps her alive upon being skewered by the Gate of Babylon. She can also direct all of her magical energy into healing herself. If she is too damaged, she will be unable to manipulate the external energy, no matter how much is present.

She can also use an extremely strong version of Reinforcement on regular humans, greatly strengthening them and allowing them to harm spiritual bodies like Servants. This allows for Kuzuki to slay Rider and almost kill Saber due to his unique fighting style. If he were to go against Caster for some reason, the battle would come down to whoever manages to get the first strike.[8] She cannot utilize a Reality Marble, but she can potentially construct "another world" of the same scale by precisely constructing small magecraft and large magecraft. The time and expenses required to do so would be very vast.[9]

While she is from the Age of Gods when True Magic was common, she is incompatible with the "Five True Magics of the Modern Era", and she would be unable to learn them.[10] She does display Tροψα (Trofa) ( 空間転移トロイア ,  Kūkan Ten'iToroia ?), a Spatial Transportation spell that is an imitation of the True Magic governing teleportation much like the teleportation granted by Command Spells. She can use it while in her territory, but she also displays the ability to teleport throughout the rest of the town as she wishes. She is able to transport Kuzuki at the same time by encircling him with her robe. She can also transport other people to her from far away, allowing her to bring Shirou to her from the mountain steps. Saber is unaffected due to her Magic Resistance.

Castermirage

Caster covering herself in magical energy

She is able to manipulate her figure and her robe in a number of ways. She can control the magical energy in the air to become a dense fog that covers her entire body. This allows her to manipulate her appearance by covering herself in darkness like a mirage. Looking like a shadow that reminds Shirou of Death, she can show herself as she wishes or remain hidden from sight. She can create solid images of herself that will fade away as if she were actually killed upon being attacked. She can control them from a long distance in order to manipulate her Warriors, or she can do it while in battle to create a diversion for her attacks. Upon being skewered by Gilgamesh, it seems she has died, but she is able to hide herself in her floating cape in an attempt to escape. She can extend her cape as wings for flight, which allows her to maximize her destructive potential with the Rain of Light.

Caster has a high rank in Item Construction, allowing her to manufacture a variety of magical items. She can make Mystic Codes for combat, but she thought it would be too time consuming and instead focused on fortifying her Temple. The difference in quality between Mystic Codes forged by her and those of normal magi is like heaven and earth.[1] Her rank makes her capable of creating healing potions that grant limited immortality, and she is capable of turning humans into formal tools to support her magic. She takes an interest in Shirou Emiya, calling him a "rare specimen" with an incomplete unique ability that is more interesting than someone who leans more towards "complete omnipotence" like Rin. She makes an "Artificial Noble Phantasm" out of him by removing his limbs and using him as a wand for Projection magecraft.[11] During the "Hazy" bad ending, he is shown to be thoughtlessly trapped in some form of container filled with water like an embryo in a test tube. He dies after the container is smashed by Rin.

Typically, Heroic Spirits of an evil nature like Caster are not eligible for participation in the Fuyuki Holy Grail Wars; however, after the Holy Grail was tainted in the third war, most of the restrictions against such spirits were lifted.

She can create Dragon Tooth Warriors to act as basic soldiers to attack enemy Masters and Servants.

CombatEdit

Caster lacks any offensive Noble Phantasms. She only has access to Rule Breaker, which is a ceremonial dagger unlikely to be able to kill even a regular human. Its main use is as an Anti-Thaumaturgy Noble Phantasm capable of dispelling and destroying any kind of magecraft. The greatest benefit it offers during the Grail War is the ability to sever the connection between an enemy Servant and Master, allowing her to take their Command Seals for her own. While she also has access to Argon Coin, she does not have the capability to utilize it. It normally would allow for the summoning of a dragon, but she lacks the necessary spells to summon Phantasmal Beasts. It has been given the status of an unusable skill during the Fifth Holy Grail War, but if she did have the proper knowledge, it would raise her standing from the weakest of the Servants to the middle ranking.[12]

She cannot fight directly against the other Servants as a Caster. Due to the natural Magic Resistance of Saber, Lancer, and Rider, she is unable to match them in direct combat as a magus. She instead resorts to using tactics such as breaking the rules of the war to summon Assassin, creating her territory to collect souls from the town, and staying out of the fight herself so that she can observe the progress of the war before making her move. Under normal conditions she may have restrained her Master like a puppet to further her plans, but her love for Kuzuki and his apathetic view of the war allows her to make all of the decisions without resorting to such a tactic. If forced into combat, she does have confidence in her own abilities. She claims that she is stronger than anyone besides Berserker and Saber, and she states that Archer wouldn't be able to even scratch her. She is quickly proven wrong when Archer easily uses two attacks capable of killing her, one of which he even warns her to dodge.

She is not a threat in a direct confrontation like Berserker, but rather the most troublesome enemy able to worsen the situation without even showing herself. Her main goal is to prolong the time she can spend with Kuzuki, so she is mainly working hard for what comes afterward rather than forming strategies to deal with the other Servants. She uses her defensive position to have Assassin fend off the other Servants while she makes her plans. During Fate, she doesn't make a move until Berserker is defeated, and during Unlimited Blade Works, she makes a move against Shirou upon finding that he is a weak magus so that she can obtain Saber. She wishes to gain allies, so she claims that she can prepare a better Servant superior to Saber for Shirou and a magus superior to Rin as a Master for Archer.

She has a method of winning the War Holy Grail War instead of the regular fashion of destroying all seven Servants. She has grasped its true nature, and seen past the pretense that it is an only a ritual to grant the wish of one winner. She knows that it is meant to forge a path to Akasha, and that Servants are summoned only as catalysts to create that path. Even though it is impossible for other Servants, she can see the trick behind it because she is a Caster and claims that it is easy for her to win at any time. She is prepared to do so once she has the proper tools behind her, and makes the claim that she can summon it at any moment with the help of someone with an enormous magical energy output like Saber. Upon Shirou's cooperation during the "Hazy" bad ending, she is able to obtain it and seemingly win the Holy Grail War.

Caster's natural enemy is Berserker, and she feels that she will be unable to defeat him without taking control of Saber. Even with support from Kuzuki and Assassin, her two front-line Saber-class defenders, she would only be able to damage him two or three times before her high-level magecraft would become ineffective. She is capable of supporting Assassin against him by weighing Berserker down with her magecraft, but that is only effective in repelling him from the mountain gate.[13]

Against humansEdit

Castercontrol

Caster controlling Issei

In a competition against humans, it can be said that she is the most dangerous opponent capable of bringing about the most horrifying and greatest results of all the Servants summoned during the Fifth Holy Grail War. Aoko Aozaki, a user of True Magic said to be capable of battling Servants in direct combat, and Ciel, who has a magical energy capacity one hundred times greater than an average magus and knowledge inherited from Michael Roa Valdamjong, would be completely outmatched in a full out battle of magecraft. Bazett Fraga McRemitz, who can potentially slay Servants with Fragarach and has the capability to dodge, deflect, or nullify high thaumaturgy, would be quickly fatigued before being able to get a chance at getting an advantage in the fight.[14] If Ciel were given cooperation from the Association and the Church, allowing her to get her hands on Gazamy, who lies in the deepest parts of the Evocationary area of the Association, and the Seventh Holy Scripture, the battle could have a different outcome.[15]

She can easily control humans and weak Magi like Shirou, and her degree of power allows her to take control of even a magus' body from kilometers away. Due to this, she can easily control anyone in the town from her location. While another magi would have to normally infuse their own magical energy into the enemy to gain control, Caster is able to take hold of someone with one single cursed word. Normal practice would allow the target fight off such control by forcing the enemy magical energy out with their own, or by concentrating all of it to one limb so they can regain control of the other three. Caster's use of a single completed spell inserts only a "poison-like element" in one small point on their chest rather than mixing her own magical energy into their bodies. It is potent enough that it feels as if there is something wrong with their blood vessels themselves, which affects the target's entire body by taking authority over it away from the them. This makes it impossible for them to regain control over their bodies, as trying to wash away something "solid" like a completed spell with a "liquid" like magical energy is not possible for modern magi.

She is able to call Shirou to her all the way from the Emiya residence simply by commanding him to "Come" repeatedly with a magic-infused voice. Normally controlling him would be impossible even with his weak magic resistance, and doing from that distance is even more astonishing. It seems like a dream to him initially, but he eventually realizes that his limbs are not moving under his own will. Without any resistance, he walks all the way to the temple in a daze while his limbs are manipulated. Even once fully conscious, he is unable to stop himself, and he is unable to even scream due to his throat being frozen. The only way for him to regain control is for her to release him from the spell or to receive outside help. Once given control, she can skew their senses, distorting the vision or rendering them blind. She can eliminate their bodies or minds in a matter of seconds, which allows her to destroy Shirou's mind while keeping his body for her own use. She is capable of churning his insides from a simple whim, and then completely stops his senses and ceases his mind.

She can also easily turn humans into "dolls" for her own use. Using "artificial Command Spells", she instills her control upon all the people at Ryuudou Temple. They become "things" that execute a single command when they find someone that breaks one of the "three rules" she has established. Upon asking Issei Ryuudou about Caster, he immediately blacks out and slashes at Shirou's stomach upon getting back up. Caster is able to speak through him, and mentions that the implanted order only functions when someone inquires about her. She is also able to manipulate them further, which allows her to have Issei kill himself by stabbing his own neck.

MasterEdit

She is capable of easily breaking the rules of the Holy Grail War by slaying the original Master who would have summoned Assassin and summoning a Servant of her own.[16] He is an Assassin summoned by an improper Master, so someone other than the proper Assassin, one of the Hassan-i-Sabbah, was summoned. Spirits cannot form proper contracts with other spirits, so only her knowledge as a magus allowed her to form the connection. The results are poorer and more ineffective than under conventional circumstances, so she summons a fictional hero who is based on a wraith rather than a true Heroic Spirit.

She had something similar to a Command Spell. Though, as a fake Master with a fake Servant, it wasn’t something as powerful as a true Command Spell. While she may not originally have received any Command Spells, Caster may have skillfully borrowed the power of the Greater Grail to forge herself an imitation.[17] As with other Masters, she is able to forcibly remove Command Spells from a Master by severing their arm and all the nerves in their bodies in order to transplant the Spells and become the Master of their Servant. If she can come into contact with the Servant, Rule Breaker allows her to obtain the Command Spells much more easily. Through those methods, she can take control of as many Servants as she wishes due to siphoning energy directly from the land, allowing her to her to act as the Master of Saber, Archer, and Assassin simultaneously. She thinks Saber is too valuable to disappear, so she make it her main goal to obtain her. She is unlucky with Saber, as her Magic Resistance is great enough that it takes two Command Spells to immediately force her to do any task that she doesn't wish to follow. Caster doesn't wish to waste them, so she is forced to wait a great deal of time for Saber to finally reach the breaking point from the initial command.

TempleEdit

Caster has a high rank in Territory Creation, allowing her to use the Ryuudou Temple and surrounding mountain as her Temple. It is a very suitable place for her, as it is the greatest spiritual land of Fuyuki City that holds many of the leylines of the area. It is unfavorable for Servants and it allows her to easily draw energy from the land and the citizens of the city in order to provide her with a nearly limitless amount of magical energy. She compares it to having one thousand Masters, and she has enough energy that she claims to be able to have Saber use Excalibur as many times as she wants. She has placed a magical string throughout the town for this purpose, and she has taken control of the leyline with sacrifices. It is also considered on of the four main areas where the ritual of advent of the Holy Grail can take place, which guarantees her the ability to summon the Grail once the conditions are met. It also provides for the greatest defense in the city due to a strong barrier that was likely set by those who first constructed the temple.

The entire mountain is surrounded by a powerful Bounded Field, Ryuudou Temple's Barrier (柳桐寺結界, Ryuūdō-ji Kekkai?), that rejects unnatural spirits that set foot around the area. Servants attempting to cross it will have their powers reduced, and the effects of Noble Phantasms are also greatly diminished. Caster has also set up her own anti-sorcery Bounded Field (対魔術の防御結界, Tai-Majutsu no Bōgyo Kekkai?) to greatly diminish the effects of outside magecraft as well.[18] Humans and magi are unaffected, allowing them to enter anywhere on the mountain without any problems. The effects of the Bounded Field only affect those that directly cross the boundary line, and it has no affect on those directly inside the Bounded Field itself. Once inside the temple, it acts as a suitable place to sustain spiritual entities, which is one of the reasons Caster managed to avoid disappearing before establishing a contract with Kuzuki.

It is impossible to fully close off the area with the Bounded Field, as the leylines require a connecting point with the outer world in order keep them from being halted and rendered unusable. The only weakness in the barrier is the temple's front gate and the path leading to it up the mountain, which acts as the focal point of the leylines. This allows for Servants to enter through the gate undiminished as long as they follow the main path up the mountain. Caster has covered this weakness by placing Assassin there, and due to the terrain advantage and his own skill, he manages to repel all five enemy Servants. This specific location was chosen due a policy of the temple’s monks in which they do not refuse entrance to anyone who walks through their front door.

The method she uses to take the energy is through a witches potion that destroys love. It takes their magical energy and renders men impotent. It leaves behind the smell of a rotten plant, and it can render a large number of people in various areas in comas. Rin finds fifty people, most of which are men, who have thrown up blood and fallen unconscious at once. The large number of people placed into comas is attributed to gas leaks causing people to pass out after running out of oxygen, which have been ongoing since before the formal start of the Holy Grail War. When she first began to collect the energy, it was hard for her to hold back because each individual only has a small amount. The result was that she ended up taking too much at a time, but she likes to keep her victims alive so that she can take every bit of magical energy as possible. She eventually managed to begin collecting it much better, allowing her take energy from hundreds of people at one time. The swirl of preserved magical energy, pieces of people, is collected within the land and used by Caster. Shirou sees that it is made of more than a thousand souls that stain the entire mountain in energy.

He is an unorthodox magus who makes use of a very specialized version of Projection magecraft. Shirou is initially completely inept as a magus, only able to use Reinforcement and Projection Magecraft with a low level of success. Reinforcement allows him to analyze the structural composition of an object, and increase its effectiveness, such as making it more durable or its shape more practical, or return it to its original state. He can also use it to improve upon the physical capabilities of his own body, such as his eyesight, allowing him to see as far as four kilometers away. Shirou is also very skilled in Structural Grasp Magecraft, which allows him to understand the structure and design of objects as if he were viewing a blueprint. Projection, while a high level skill, is generally considered useless compared to Reinforcement due to the higher magical energy cost, and anything that Shirou initially projects is useless and hollow. Though the objects merely imitate the shape, there are only a few who can identify them as fakes in a first glance. Any practitioner that analyzes composition wouldn't be able to see through them, and even one that works through spiritual mediums would only notice a sense of incongruence. Since only objects with history ever go into the Department of Spiritual Invocation of Clock Tower, there is a low probability of them being discovered. Shirou's structural analysis is not a type of Mystic Eyes.[8]

Shirou is later capable of using Tracing, a higher level version of Projection that completely copies everything regarding the creation and existence of the object. During the Fate scenario, he slowly learns of it on his own by training with Rin and following Archer's advice: "If you can't defeat it, then imagine what can", while in the Unlimited Blade Works scenario, he learns of it through extensive contact with Archer. He is only effectively able to reproduce swords, other weapons, and armor, but this specialty allows him to faithfully reproduce even legendary weapons. He is capable of reproducing any sword that he has seen, though Noble Phantasms are always one rank below their original strength and armor costs three times the amount of magical energy, and he is capable of employing its entire history, allowing him to wield any weapon with the same proficiency of its original owner. He has to see the weapons as how their form as final product actually are with his own eyes to reproduce them, as even the blueprint of Zelretch is not enough to reproduce it, but by seeing it and Caliburn through shared memories of Justeaze Lizrich von Einzbern and Saber, he becomes able to fully trace them afterward. If the weapon is not made of materials that exist in the world, such as Ea, he cannot analyze or reproduce it, though he can tell its basic nature. He is also quite capable of creating his own original kinds of weapons, should he put his mind to it.

RinShiroucontract

Rin forming a contract with Shirou in Realta Nua

It is later identified that these abilities and Shirou's affinity with swords are concepts of Shirou's Reality Marble, Unlimited Blade Works. Rather than simply creating his projections in the real world, he actually reproduces them within the Reality Marble, as if he were loading a gun, and then projects them into the real world as if he were firing it. This allows him to prepare dozens of swords at a time for later use. Shirou is unable to properly deploy or maintain Unlimited Blade Works due to a shortage of magical energy, but with a proper contract with a magus with a suitable level of magical energy, such as Rin, he is capable of using it. If he were to learn about it normally, unlike the situation in Unlimited Blade Works where he learns of it firsthand from Archer, it would take ten years of training to set the foundations for the ability and another ten years to reach to the point of being able to use it.[9] While actually using Unlimited Blade Works, the cost for creating the weapons is greatly diminished and the speed at which they can be created is also increased, allowing him to easily overwhelm Gilgamesh and his Gate of Babylon.

If Shirou were to fight Shiki Tohno, there would be a high probability of a mutual defeat where Shirou would have his projected Noble Phantasms one-sidedly killed, while Shiki would overuse his Mystic Eyes of Death Perception to the point were he would overload and self-destruct after the battle. Circumstances would change if Shirou were capable of an Excalibur-like magical energy discharge. During a fight with Bazett Fraga McRemitz, a professional that specializes in anti-magus combat, he would likely be overwhelmed by her techniques, experience, and tactics, and he would also constantly have the disadvantage that using any of his high level techniques would leave him susceptible to Fragarach's instant kill ability.[10]

KnowledgeEdit

Shirou Archer Arm

Shirou with Archer's arm preparing to use Nine Lives Blade Works.

Shirou's basic training in Magecraft was extremely lacking, so he was left with the idea that he needs to create a new Magic Circuit with each use of Magecraft. He goes through extremely dangerous training, which he describes as the feeling of inserting a hot iron rod into his spine, where he constantly faces the risk of death in order to develop a new Circuit. Though his body has twenty-seven natural Magic Circuits, they had been abandoned for his nerves, which he made into makeshift Magic Circuits due to his wrong method of training. Once his real Circuits are awakened, he goes through extreme pain and suffering as his nervous system gets used to the new intake of energy. His newly opened Magic Circuits can barely handle ten units of magical energy each.

Shirou has Avalon implanted within his body, which saved his life during the great fire. This gives him an extremely potent regenerative ability while Saber is summoned due to Excalibur, though it does seem to sustain him even without it as he was able to temporarily survive a fatal blow dealt by Lancer. This allows him to survive numerous fatal wounds though it works against him in bad endings where he is able to be tortured and mutilated without succumbing to his injuries for a long duration of time. Unlimited Blade Works also seems to protect Shirou by creating blades within his body to reinforce it. He is able to survive a blow to the chest from Rider's dagger, which is repelled as if it is hitting metal, a kick that would have gouged his stomach only knocks him away, and he manages to keep from having his entire body destroyed from an attack by Gilgamesh. The ability seems to go out of control during a bad ending where numerous swords sprout from his dying body, and while his body is fully breaking down in the Heaven's Feel scenario, they are constantly being created and protruding from his skin.

He practices basic sword fighting with Saber, though it amounts to little in actual offensive capabilities. While she teaches him, he cannot use her fighting style as a model. He cannot see exactly how she is attacking and their different physiques makes her impossible to copy.

FateEdit

During Fate, Shirou only learns the basics of his abilities, leading him to only trace Caliburn and Avalon.

Shiroubow

Shirou's Bow

He temporarily utilizes a bow during the second battle with Berserker, having imitated Archer's Bow. Shirou’s Bow (士郎の弓, Shirō no Yumi?) is formed by utilizing strengthening magecraft on a tree branch he had found, and he creates arrows for it in the same manner. It utilizes the same design for the most part, but the arrow rest and grip are amateurish and simple compared to those of Archer's bow. Shirou personally thinks it is ugly and crooked, but it functions properly as a bow. It is also slightly less curved due to Shirou's preference in the Japanese method of shooting. He is only a practitioner of Japanese archery compared to Archer's Western method, so he subconsciously altered the bow into his preferred shape without realizing it.[11]

Unlimited Blade WorksEdit

ContradictionEdit

Shirou and Archer's connection is a large part of his development in the Unlimited Blade Works scenario. The contradiction of Shirou Emiya and the Heroic Spirit EMIYA existing at once is much like magecraft that allows one to acquire skills from the past by possessing themselves with a previous self. The more they come into contact, the more of his knowledge and techniques flow into him. The abilities suit him perfectly, as they are Shirou Emiya's optimal technique, perfected over many years of training.

It is first noticed after several training sessions with Saber, when he makes a drastic improvement over the previous day. Copying Archer's technique, he begins to make fewer unnecessary movements, allowing him to desperately avoid her counter-attacks rather than become instantly knocked out, and as his body is already fit, just the knowledge of proper techniques can improve his fighting quickly.

He is captivated by Kanshou and Bakuya, and uses it as a basis for a two-sword fighting style. He does not have a basic style, so it is immediately evident that he is copying Archer. The flow of it is so unconscious that he believes that Saber is going easier on him, and his sword is able to automatically parry her strikes even though his body cannot react to them.

The effect greatly magnifies after they recognize each other's identities, causing extreme pain as it flows into him. His body begins to break every time they touch, as he has learned too much of his future self while trying to match him in skill. He even begins to obtain Archer's memories, such as the reason behind his hatred for their shared ideals.

ProjectionEdit

Once he learns the true use of Projection, he lacks proper training so even the most basic projections cause him pain and the majority of the swords generated shatter upon impact due to their low quality. He projects both Archer's sword technique and his reproduction ability, but it is flawed because he does not understand that they originate from his Reality Marble. Unlimited Blade Works cannot be utilized without that realization, and even after coming to that conclusion, he does not have the necessary energy to utilize it on his own.

He forms a contract with Rin to have her provide the necessary magical energy to form his Reality Marble and he manages to project a number of weapons from the Gate of Babylon while fighting Gilgamesh.

Heaven's FeelEdit

Archer's armEdit

Shirou does not develop his abilities as he does in the other routes during Heaven's Feel. He uses his basic Reinforcement magecraft on a stick and wooden sword during the early part of the war without grasping onto Projection. During the first conflict in the Einzbern Forest, he loses his arm while protecting Ilya from the Shadow's explosion. The wound is critical, so Archer, having also suffered a critical wound, tells them to transplant his left arm onto Shirou. Attaching a spiritual body to a normal human body requires a spiritual doctor like Kotomine because the process it more akin to healing the soul rather than the body.

Kotomine manages to attach Archer's arm (アーチャーの腕, Āchā no Ude?) to replace Shirou's lost arm. It is a "foreign substance" that should not be there, attached by opposing the natural Providence, and joining two separate spiritual bodies is forbidden magic that cannot normally succeed. The formation of spiritual bodies deals with resurrection and restoration of souls, divine mysteries that cannot be handled with magecraft, so it would normally be that the recipient would die of shock even if the operation was a success in shape. Kotomine expected the completion of the surgery to result in his death, but Archer and Shirou being the same person makes them an exception to the normal rejection. Not knowing of their exact connection, he states that they are suited for each other and not even two twins would be as similar.

While the arm would have disappeared had Archer faded away while the surgery was in progress, it is now anchored to Shirou and can be called his own limb. Due to being transplanted while Archer was still in the world, it is part of a Heroic Spirit that has been connected to his Magic Circuits, and stays in the world using his own magical energy. While unconscious, the arm grants him knowledge on Archer, the basis of Projection magecraft, battle experience, and battle information. The sensation feels like his body is burning while countless ants enter the hole in his shoulder that is now sealed with flesh that is not his own. While the sensation tells him to manage these skills, the level of information and power required feel impossible to him. Even if it becomes familiar with his body, he neither has the skills to handle it or the power to use it without destroying his body.

While they are the same person with compatible Magic Circuits, the power of the arm of a Heroic Spirit is not something a human can handle. No matter how suited he is to the arm, he cannot use its abilities without it eventually swallowing him due to his body being spiritually far inferior to the arm. It can be considered a weapon more than an arm, and it is referred to as an Artificial Phantasm: Man-made illusions ( アーティフィシャル・ファンタズム人工的な幻想 ,  Ātifisharu FantazumuJinkōtekina Gensō ?) in the scene's title. It passively flows Archer's battle experience and physical abilities into Shirou even while inactive. It acts like an overdose of strength-enhancing drugs, letting him demonstrate abilities beyond his limits.

He becomes able to easily leap out of the third story window of the Einzbern Castle, compared to around eight stories for a normal building, with only temporary numbness and pain upon landing. Unable to strengthen his body, he does bring a large amount of magical energy to his feet to lessen the impact and believes that landing on asphalt instead of grass would have broken his legs. Ilya mentions that Archer is influencing both his mind and body, making him think that he can easily handle the drop like Archer and toughening his body enough to survive. He can also run fifty kilometers per hour through the uneven terrain of the Einzbern Forest.

Shroud of MartinEdit

ShroudofMartin

Shroud of Martin

In order to counteract the effects of the arm, Shirou is given a Holy Shroud, the Shroud of Martin (マルティーンの聖骸布, Marutin no Seigaifu?), by Kotomine, as a seal which keeps Archer's circuits from connecting to his body because it has the ability to seal a certain event or return it to normal.[12] It completely wraps around his arm with the exception of his fingers, and while it is initially completely numb, it eventually regains enough functionality after familiarizing with his body to allow him to lead an ordinary life. It would be possible to cut it off, but that would remove his only possible weapon in defeating Zouken.

The arm is treated as a different object even if he uses magecraft, but magical energy still constantly flows through the body even if magecraft is not being used. Despite the Shroud cutting off the Magic Circuits, he will feel a great deal of pain if he does not concentrate to form a "barrier" to keep the "foreign substance" out of his unstable body when the arm reacts to the energy and tries to activate. It is easy to do once he figures out where the pain is coming from, and he is able to control it to an extent. Living with it is not quite as easy as Kotomine suggests because the arm randomly flows magical energy into his body. It constantly becomes hotter each time he moves it, and when it overheats, it sends the excess to the rest of his body.

While it first feels like he is being burned, he realizes it is more like he is being cut and stabbed by his own body. Simply undoing part of the binding for even a brief moment causes him to completely lose himself as his nerves and senses are overwhelmed by extreme pain and the feeling of impending death. He rambles on in his mind about how he is feeling more pain than ever before, "sitting on a mountain of swords", and that he can see all of his cells crumbling apart. He regains his senses a few seconds afterward, and he cannot remember the exact happenings during that period.

He is able to manage at times, but also suffers a great deal of pain in intervals to the point of wishing to simply cut it off, or even risk removing the shroud to stop the pain. Its existence brings him true fear of an unavoidable death and utter obliteration, making it the first he has felt such since the fire ten years before. His ability to suppress the infringement from the arm even with the Shroud is limited to a certain extent. Kotomine believes that the arm will consume him within ten years, but it is possible for him to live to an old age if he trains to become a magus worthy of matching the arm in order to seal it without the Shroud. It is not an imminent threat, so he would have enough time to attempt do so if he wished.

Rin also shares part of her Magic Crest with him as a Warding Sign. She is able to transplant a small part of her Crest by placing her left hand on his body, comprehending it, and sharing her warding crest. While she was planning on giving him the capability to use a "switch" for his Magic Circuit, being able to turn it on and off is too dangerous in his current state. She instead performs it to suppress the magical energy by placing needles in his left shoulder, belly button, and throat so that the arm won't be connected to him unless he wishes for it. It also grants a resistance to magical energy, so that something that passively absorbs energy like the Shadow will have less of an effect on him. Her crest cannot familiarize itself with someone not from the Tohsaka family, so it is a makeshift that won't even last a week.

ProjectionEdit

Shirou is currently observing Archer's magecraft rather than his own magecraft, so he cannot use Projection in his current state without invoking the abilities of the arm. Ilya states that he will eventually obtain his own usage of Projection magecraft, but it is still only a possibility at his current level. His own Projection is still at the level where it will fail constantly due to his misunderstandings, but drawing on Archer's knowledge without invoking the arm can force him to "level up" quickly. He can loosen the Shroud slightly in order to practice retrieving Archer's knowledge without breaking the seal and only getting a small reaction.

With help from Rin's Magic Crest to increase his Magic Resistance and Ilya to protect his consciousness, he is able to experience Archer's Projection by interacting with the arm like opening a Magic Circuit. The knowledge is like poison, but the arm will continuously flow its experience into him. It is similar to pouring one hundred units of fuel into a container that can only hold ten, and he will likely only gain from less than a tenth of the agony he will endure. The knowledge disrupts his memories and leaves him with a large blank space after replacing the Shroud.

Projecting directly with Archer's abilities requires the removal of the Shroud, and while he may be able to recall the activation spell gained from Archer's knowledge, it would destroy his body to attempt using it. It can easily be removed at any time for instant access to the full extent of Archer's power. It is not something that lessens his life with each use, but the activation of a time bomb that will ultimately lead to his death the second he removes the Shroud. Archer's Magic Circuits will be activated if he uses the arm even once, and while he may last while using its abilities, his body will break down due to being unable to withstand Archer's magic. He will eventually be consumed, or more correctly "blown away", by the arm after the first activation.

Once it is removed, Shirou instantly gains access to Archer's Magic Circuits, battle experience, and techniques, but he cannot deploy Unlimited Blade Works because Archer's inner world is different from his. He claims that he can only reproduce what he himself has learned and the Noble Phantasms that he has personally recorded, but he is later shown to be able to project Caladbolg II and Rho Aias from Archer's records despite never having personally witnessed them before. His Projection magecraft allows him to match Servants in direct combat for a limited time and even defeat them. He is able to trace "Nine Lives" to kill Black Berserker nine times with a single maneuver called "Nine Lives Blade Works" and later defeat Saber Alter with the Overedge technique of Kanshou and Bakuya at the cost of his mind during a bad ending. Using these abilities comes with a heavy penalty as Archer's circuits overload Shirou's body leading to his mind slowly eroding, the decay of his memories, and eventual death as his body and soul break down from being invaded by Archer's Unlimited Blade Works.

Puppet bodyEdit

Due to Archer's arm and his overuse of Projection, his Magic Circuit is broken into pieces, and his death is one that even the Holy Grail could not reverse. He is resurrected by Ilya's imperfect usage of the Third Magic, reviving his soul and giving him a body free of wounds by preserving his soul and inserting it into a container. It would normally be that giving the soul a container or body would allow it to take perfect form by utilizing the "genes of the soul" rather than those of the body. His body is reconstructed from a portion of Ilya's body, which she mentions is a bit cheap as a container, so it is nowhere near his original form in terms of size. Its shape afterward is not that of a human, but as he mentions reaching his hands out and grasping onto Rin's pendant, it is at least vaguely humanoid. He is able to be found due to Rider using the pendant as a landmark to locate him, and while his exact form is left unknown, it is small enough to be "plucked" from the river by Rider.[13]

He is not a true product of the Third Magic, a high-dimensional planar being, but it instead re-anchored his soul to a vessel. They decide to experiment with various ideas for a proper body during the first six months, as he cannot simply grow in his current state. They do not have the resources to make a homunculus body, so they instead sell the books of the Matou household to obtain a puppet body left by Touko Aozaki. He is perfectly human even in this state, but Rin notes his soul is actually remotely controlling the body. He can receive surgery at hospitals, drink cold medicines, be killed, and eventually grow old and die of old age. The soul is fixed to the body, so he can be likened to a Servant that can operate without a Master.

He has some issues because body is used, but even other good puppet makers cannot match up to it. Rin wishes to find and consult Touko about it, but her Sealing Designation makes that a hard prospect. The magical energy does not flow well, but Shirou is fine with it because all other aspects are better than his original body. The soul will overwrite the body no matter its quality, so there will likely always be places that won't function properly. Sakura supplements his very weak Magic Circuit with her own overflowing amount in order to keep him from returning to his prior state. Despite the setbacks, Rin believes that he should be able to utilize Unlimited Blade Works with training, and that his being a successful example of the Third Magic is an extraordinary trait in itself.