|Title:||Bounded Field of the Wind King|
|Maximum number of targets:||1 object|
Invisible Air: Bounded Field of the Wind King (風王結界, ?) is a sheath of wind that covers Excalibur and conceals it so that it cannot be easily recognized as the famous holy sword of King Arthur and expose her identity. It is a bounded field closer to magecraft than a Noble Phantasm that is made up of multiple layers of wind compressed into super-high pressure air with a massive amount of prana, which distorts the refraction of light and renders what is inside completely invisible. While it has no basis in history, Kinoko Nasu figures it would be something Merlin could have managed because Heroic Spirits with overly famous Noble Phantasms generally have ways to hide their identities.
Upon Excalibur, it takes on the shape of the blade and renders it as an invisible sword that doesn't appear even as sparks fly off of it. It lacks the capacity to annihilate the enemy like Excalibur, being more suited as a "sharp tool" in battle. It isn't used for any particular strength, but it is easier to use in battle than Excalibur and it is a trump card that can bring about victory if used well. It is also possible to implement the barrier on something other than the sword. She can form the barrier in the area around her or as a quick defensive wall of wind, which she can keep active for a number of minutes with her magical energy. She uses it in Fate/hollow ataraxia to completely envelop the entire central building in an unbreakable protection. She releases it like an arrow to cover the body of her Yamaha V-Max motorcycle in Fate/Zero. Using the compression of the pneumatic umbrella surrounding her, she decreases the air resistance to zero to increase the vehicle's speed and keep the back wheel firmly against the cement with the pressure.
It is rather simple in execution, but it proves tremendously effective in hand-to-hand combat. The barrier isn't a vacuum, so the air constantly whirling around the blade is essentially a weapon. It increases the damage and cutting power of an attack, and the amount of prana released from each strike is high enough that it is visible to the eye. It also provides for an increased accuracy and defense against opponents unfamiliar with the nature of her weapon, as it is difficult for the opponents to parry lunges and thrusts from Saber. They cannot discern the length, width, reach, or trajectory of the blade, or even the fact that it is even a blade until they actually make contact with the weapon, which leaves them constantly on guard due to having to rely solely on Saber's movement to decipher her attacks. They are confused both offensively and defensively, only allowing them to approximate the movements of the strikes and keep outside of her range to avoid being easily struck down. Against an opponent who can figure out the nature of the weapon quickly and correct the visual disturbance, such as Assassin with his "Eye of the Mind (Fake)" ability, someone who already is familiar with the weapon, such as Berserker, or someone with a resistance to visual impediments, it becomes nothing more than wind around a sword.
Once the barrier is released so that Excalibur can be used, the previously compressed wind surges around her chaotically, creating a vacuum as it diffuses into the air with enough force to knock over normal people and shake heavy, firm trees like a typhoon. The compressed wind can also instead be released as a single use projectile weapon called Strike Air: Hammer of the Wind King (風王鉄槌, ?). Acting like a hammer made out of wind, it creates a gale made out of super high pressure condensed air that is powerful enough to easily crush and blow away armies and fling a stone slab weighing several tons into the air as if it were nothing. It is a long range attack with a constant amount of damage that in not influenced by Saber's physical condition or her level of prana. It can only be blocked by overwhelming it with a higher amount of prana. It can also be used to accelerate her own body towards her opponent, allowing her to travel at three times her normal speed. By holding the sword in a backward wide stance, she releases the air and changes into a supersonic bullet that charges towards her opponent. If working together with another person, the partner can use the vacuum left behind by the attack to immediately rush in behind it by using the surge of air taken in by the vacuum as a slipstream. After releasing it, she can recall it by compressing the surrounding air to reform the barrier.
Fate/complete material III: World material - FAQ with Nasu: Noble Phantasms, p.134
Q: What did you have in mind when you created these original Noble Phantasms (“Bounded Field of the Wind King: Invisible Air”, “All-Violating Talisman: Rule Breaker”)?
Q: Though many Servants possess Noble Phantasms that appear in their actual myths and legends, there were some that felt like original creations for the game. What did you have in mind when you created these original Noble Phantasms (“Bounded Field of the Wind King: Invisible Air”, “All-Violating Talisman: Rule Breaker”)?
A: Invisible Air was simply a form of sorcery meant to conceal a Noble Phantasm. I thought that surely Merlin could have managed that somehow! Heroic Spirits that possess overly famous Noble Phantasms have a trick or two to hide their true identities.
[As for Rule Breaker,] I created it from her image as a treacherous archmage. I figured she would be too weak with only her Dragon’s Teeth soldiers.