Command Spells

The Command Spells (令呪) are three claims of absolute obedience, the crystallization of a great magic, that a Master has over a Servant in the Holy Grail War system. Unable to normally be controlled by humans, they are burdened by the "absolute condition for materialization", the authority of the Command Spell carved into them at the moment of summoning. They are holy marks signifying a magi's status as a Master, a system that was created by Zouken Makiri after the failure of the First Holy Grail War. Only known to the Three Founding Families and Supervisor, their truest purpose is to allow the winner of the Grail to force the Servant to kill themselves so that the ritual to reach the Root with all seven Heroic Spirits can be completed.

Obtaining Command Spells
The Fuyuki Holy Grail grants a total of twenty-one Command Spells in each war. Masters obtain three Command Spells, and Servants have no choice but to cooperate with their Masters due to their hold over them. Depending on the nature of the Servant, such binding is not necessary, while others may slay their Master instantly should all three be lost. They disappear as they are used up, and it can be said that a Master who uses up all three loses authority over their Servant. Even if a Master contracts with multiple Servants at once, they will only be given a total of three Command Spells that can be used on any contracted Servant. It is possible to steal more from other Masters or receive more from the overseer depending on circumstances, and it is also possible that anyone interfering with the activities of the Church will have their Command Spells decreased. Their loss does not indicate forfeiture of position in the Grail War, as the contract with the Servant is also part of being a Master.

Once all Command Spells have been given out, or even if fake substitute Command Spells are created in the case of Caster's contract with Assassin, new proper Command Spells will not be created with the addition of a new contract. Command Spells do not disappear simply with the loss of a Servant, but instead only when one gives up or loses their right to be a Master. With regular Masters, this happens instantly upon losing their Servant, and only members of the Three Founding Families have shown the ability to exercise the authority of a Master even without a Servant. They will not lose their Command Spells so long as there exist Servants without established contracts. When Kirei Kotomine regains new Command Spells when six established contracts still remain in the Fourth Holy Grail War and without him being of the Three Founding Families, it is an unprecedented feat explained only by the Grail itself having high expectations of him and the unconscious desire in his heart.

Lost Command Spells are reclaimed by the Grail during the Holy Grail War and can be redistributed to new contractors who take on a Servant who has lost their Master. While searching for new Masters, it will prioritize those who had been previously chosen. The Church provides protection to Masters without Servants for the reason of them having greater chance of obtaining leftover Command Spells. Masters aim to kill other Masters rather than simply cut off their combat effectiveness so that they will not be able to take up another contract in the future. Of the Command Spells that are left after the Holy Grail War, they are amassed in the hands of the supervisor and commissioned for safekeeping. It is possible to keep a contract after the Holy Grail War has ended, as the only issue is the added strain on the magus after the support from the Grail in the upkeep of the Servant stops.

Within the Moon Cell Holy Grail War, the Command Spells are considered part of the right to participate, so the loss of all three means immediate forfeiture even if their Servant is still alive. Masters are capable of using all three, but only two can effectively be used if they are attempting to win the war. They can freely use them on the Far Side, but would immediately be deleted upon returning to the proper Holy Grail War. As Gilgamesh is a Servant beyond the ability of the Moon Cell to fully control, he displays the ability to collect Command Spells and grant them to his Master, making him a Servant capable of destroying the very premise of the Holy Grail War.

Characteristics
Command Spells appear on those selected by the Holy Grail, some of which have been shown to manifest three years before the event. It is normal that the Grail decides on those it deems worthy and have a reason to seek it. Those of the founding families are guaranteed a spot, and if not enough people arrive to fill all seven spots, irregulars will be chosen. While those of Kirei Kotomine fully manifest on him before the war, those of Shirou Emiya first appear as a faint bruise until he summons his Servant. The shape of the seals is different for each Master; they reflect the magical characteristic of the magus. Shirou's take the shape of a sword, and Ryuunosuke Uryuu's Command Spells remind him of three intertwined snakes.

The seals typically appear somewhere on the arm, looking like tattoos at first sight. One unnamed Master in Fate/Extra mentions that his are on his lower back, negatively calling it a. Corresponding with the three uses, each has three parts to it, strokes, that fade upon usage. Once they are no longer a Master, they disappear completely, but traces can be seen. Upon receiving or losing Command Spells, there is often a slight pain. If the Master or Servant are in critical danger, it may throb to warn them.

Most Command Spells appear on the back of the right hand. Exceptions include:
 * Left hand: Shirou Emiya, Hakuno Kishinami, Shirou Kotomine, Sieg, Ruler
 * Right arm: Kirei Kotomine (Supervisor), Risei Kotomine (Supervisor), Shirou Kotomine (Extra Command Spells)
 * Neck: Wolf
 * Lower abdomen: Jester Karture
 * Whole body: Sakura Matou (Dark Sakura), Illyasviel von Einzbern, Player and Ayaka Sajyou (Right hand, left hand, right shoulder, left shoulder, back)

The Command Spells in Fate/Prototype have specific ranks and placements. They follow an motif. Each has a number of "wings" related to the appearances of the Seals, and an Angel Rank corresponding to one of the types of angels within the angelic hierarchy.

Usage
Masters must take careful consideration into the usage of Command Spells because they can be indispensable as both an emergency measure and method of governing the Servant. Depending on the relationship, they are the only thing keeping a Servant bound to them, while others will stay by their Master even without them, and those like powerful Berserkers cannot be ordered without them. Some Servants will become more antagonistic towards their Master should they attempt to bind them, so they pay careful consideration before using them. It is normal that a Master has general control of their Servant even outside of the Command Spells due to them being the anchor that ties them to the world with their magical energy. With those who have the Independent Action skill and can act independently from the Master, the Command Spells may be the only possible way to order them.

Command Spells require no incantation unlike normal spells, and the Master only needs to put their mind to it and order the Servant. Imagining the shape of the Command Spell and giving the order as they release it is enough to activate it. The proximity does not matter, allowing for it to take effect even if the Servant is miles away or through a Bounded Field advanced enough to cut off all other communication. It can be performed unconsciously if the command is direct enough, but will not be used if they are not serious about the Command. The command needs to be put into words, so removing the jaw before it is fully spoken enough to stop it. Cutting off the hand with the Command Spells just as the command is spoken is also able to keep it from coming into effect.

They are three absolute orders of unconditional obedience that can either restrain or reinforce the action of a Servant. While geas can control the actions of the recipient to an extent, they cannot take direct command of their life. Command Spells can force Servants to do anything possible for them, even committing suicide. The strength of the command depends on the Master, directness of the order, and the amount of energy it requires. Those that are broad and long lasting will weaken the power of the Command Spell. Though it will last for a long time, orders like "protect me through this" and "win this battle" will make the pain associated with the command weak enough for a Servant to disobey. Normally a command like "obey my every order completely" could not be done even with one hundred Command Spells, but a powerful enough Master can change the effect from "well, I'll respect Master's opinions slightly" to dropping them a rank if they disagree with the Master.

Commands with simple orders like "deliver the next blow with all your power" and "don't break that glass" are the most absolute of commands, and even the most powerful of Servants will find it hard to disobey. Those that both the Master and Servant agree upon are most powerful, allowing for for them to go beyond the ability to enforce orders. Supporting and amplifying the Servant, miracles beyond their normal capabilities become possible. While most cannot use Spatial Transportation on their own, ordering "go", having enough energy, and having the Servant's consent allows the Command Spell to overturn the normal methods of magecraft to make it possible to reach into the unprecedented level of Magic. Even vague orders to win that are absolutely agreed upon by both parties can have a great effect in amplifying the Servant's energy so long as they are aspired towards victory. It can allow for a Noble Phantasm to exceed its normal maximum output and perform actions beyond its normal scope like distorting cause and effect to surely hit the target. In temporarily strengthening a Servant, it converts its magical energy into energy for the Servant, enough to fill even Saber's enormous circuit.

Depending on the order, it will be impossible for the Servant to even try to resist beyond a few scant seconds of great pain. When forced to act, the Servant will use all of their abilities without any regard for their will. Like a machine, they can only watch and lament as they are manipulated. Weaker orders can be resisted at the cost of pain and decreased abilities. Those that are too broad can be almost completely ignored and have little lasting effect. Depending on the order, it will stay in effect for the duration of the Holy Grail War. It cannot be overturned by the Servant, and only the cancellation of the contract will cause it to stop being in effect. The only way to stop a direct order from a Command Spell is through the usage of another Command Spell to overwrite it. Other types of orders can be removed without such a method, such as Kayneth rescinding his order for Lancer to fight Saber and Archer asking for approval from Rin to lift her command of not harming Shirou. If a Servant is fatally wounded, an order such as "heal right this instant" will result in the wound being temporarily sewed shut with a thread of magical energy, allowing the Servant to survive for a brief period; it does not, however, provide any actual medical treatment. If a Servant is ordered to protect another person and that person may potentially seek to harm their Master, the Servant cannot work with that person unless they confirm their intentions.

While Servants can attempt to resist orders and fight against them to a certain extent, the ability to completely go against them is to "shake the very foundation of the Servant System." As they are magecraft, the A-rank Magic Resistance of Saber and Rider of Black are great enough to repulse and withstand a single stroke of a Command Spell. Saber has shown that some commands can completely overwhelm her, while she can fight back against those she is vehemently against. Against that of Caster, she is shown to be constantly under the effect and would eventually succumb with time. Given that it takes most of their strength to resist, they feel as if they are being torn apart and do not have the strength to resist a second stroke, immediately being crushed under the weight of both commands. It is possible for a Servant to lose all sense of themselves and forget the command given to them. Other means of resistance include:
 * Berserker is such a Servant that he could easily cancel the control of Command Spells of a normal Master, so he can only be controlled by Illyasviel von Einzbern's special Command Spells.
 * Berserker of Red, the "hero of rebellion" who vehemently fights against such "shackles" and possesses an abnormal EX Mad Enhancement, will only be weighed down by a single Command Spell. He won't stop his advance or obey unless two are expended, and at the maximum level of Crying Warmonger where his energy goes beyond the binds of the Servant contract, even three would not be enough to stop him.
 * Lancer of Black, after using Legend of Dracula and having Darnic Prestone Yggdmillennia's soul fused into his own, becomes a monster that can no longer be called a Servant. He cannot be bound by Command Spells in such a state, and due to Darnic's influence, could reject even a command from Ruler to kill himself.

As Command Spells and Magic Circuits are different systems of magecraft, it is possible to exercise them without the ability to circulate magical energy. The can be used and forged into highly practical magical energy that has no alignments, and enough of them can act as expandable mock Magic Crests capable of rivaling houses that have built their Magic Crests for generations. With enough Command Spells, it becomes possible to harm even a Servant.

Transference
Though they contain an enormous power and can be considered a kind of miracle, Command Spells are a form of exhaustible physical enchantment that can be transplanted or transferred through incantations. Depending on the willingness of the one losing the Command Spells, it can be done easily or forcibly with different methods. Sola-Ui Nuada-Re Sophia-Ri's method of spiritual healing can only extract them with consent from the owner. Kirei Kotomine can use Spiritual Healing with a brief moment of pain to take Command Spells willingly. Assassin of Black, admittedly not very good with transplant operations, can use her Surgical Procedure to transfer them in a process taking an hour. The Supervisor only needs to trace the marks on a Master's hand to transfer their Command Spells, but it is impossible to extract them by force with magecraft. They are protected by holy prayers, so only those who know the secret holy words may take them. Upon speaking the words, they are transferred one by one to the speaker.

As the Command Spells are integrated with the Magic Circuits, forcibly ripping off the Command Spells is roughly analogous to tearing out someone's nerves; therefore, if done poorly, the unfortunate victim can end up permanently crippled. Removing the limb and nerves containing the Command Spells allows for them to be taken and transferred at the person's leisure, but must be done before the original Master dies. No matter how superior of a magus, one cannot become a Master just by stealing a Command Spell because it it only something that can be done between Masters and Servants.

Special Command Spells

 * Book of the False Attendant (偽臣の書) - Normally a book created for magical contracts, it has been adapted to serve as a Command Spell to grant false ownership of a Servant to anyone. Created from a Command Spell, it is not the actual book that binds the Servant, but rather the Command Spell written in the book. While authority over the Servant is implanted in the book, the original Master must have at least one remaining Command Spell for it to be effective, else the fake right cannot fully bind the Servant. It is also a physical item susceptible to being burned, so it can be targeted to free the Servant. The Servant bound by it no longer receives magical energy from their real Master, so they must supplement it from elsewhere to stay manifested. It is connected to the Servant, so it bursts into flames upon their death. The rights of the real Master are given up during this period, removing their Command Spells and making them into a normal magus until the book is destroyed.
 * Dark Sakura's Command Spell - Dark Sakura's connection with Avenger grants her a large Command Spell, what was previously the Shadow, that covers her body, acting like a dress instead of her wearing clothing. It does not appear to have any immediate function, and forcibly binds her body when she begins to reject it. Using Rule Breaker on it is able to break her connection to Avenger.
 * Dead Count Shapeshifter: Dragon Revelation Command Spells - Special Command Spells gained upon taking in the heart of Siegfried, the homunculus Sieg is able to take on the form of Siegfried for three minutes per Command Spell.
 * Illyasviel von Einzbern's Command Spells - Illya, as the Holy Grail, has special Command Spells integrated with her Magic Circuit. They are incomparably stronger than normal, so they can control Berserker, who could cancel the control of normal Command Spells. It is unknown if there is a limit to the number of commands she can make.
 * Imitation Command Spells - Due to being an improper Master summoning an improper Servant, Caster does not obtain Command Spells for summoning Assassin. She instead uses the power of the Greater Grail to forge herself an imitation Command Spell that is similar but not as powerful as the real thing. Upon using Rule Breaker to steal Saber's contract, she appears to be branded with actual Command Spells.
 * Leftover Command Spells (預託令呪) - Granted to the Supervisor of the Fuyuki Holy Grail War, they are those left unused from previous Holy Grail Wars. They appear on the arm of the Supervisor, stretching from the elbow to the wrist, and far outnumber those granted to a Master. They can be given to Masters at the discretion of the Supervisor, such as a reward granted for stopping a Master and Servant who could potentially disrupt the entire ritual.
 * Player's Command Spells - The Player obtains five special Command Spells from a mysterious woman for the False Holy Grail War. The ritual lacks a seventh Saber-class Servant, but he acts as the seventh Master. They each have the ability to summon a single Servant for up to five minutes, though the time can be lessened by using up too much energy or increased by taking in energy. There are a number of Heroic Spirits that can be selected, and multiple Servants can be summoned at once. Each Servant uses up a single stroke, and they can also be used like regular Command Spells.
 * Ruler Command Spells - Rulers obtain two Command Spells for every Servant summoned in a Holy Grail War from the Class Skill God's Resolution. During the Great Holy Grail War, Ruler obtains twenty-eight Command Spells from the fourteen summoned Servants. They can also transfer Command Spells to Masters like the Supervisor, but the cannot repurpose those of Masters.