Sorry for taking so long, was in class when I got your reply. I was heavily thinking about creating a character capable of using this along with armed and or unarmed combat. Or if you have any better suggestions then I would gladly take it into consideration. The game I am currently in now already has 3 vampires, 1 lupe garou (not sure if I spelt that properly), a wizard and something else I cannot recall at the moment. I'd like to avoid being any of those if I can help it. This is Time Alter.
Innate Time Control (固有時制御, koyuu jiseigyo?) is Kiritsugu's personal application of the Emiya family's magecraft. They spent generations researching and seeking the magecraft that controls time, eventually reaching "Time Manipulation", which is the ability to separate the passage of time inside a designated space from the "flow of time" in the outside world. It is classified as High-Thaumaturgy in the form of a Bounded Field that can be regarded as a type of Reality Marble in a way, but still not something extraordinarily difficult to utilize like other time related magecraft or something on the level of the True Magic that is unable to be replicated. It allows for "time adjustment" that can only stagnate the time which has passed and accelerate time in the future rather than something more advanced like "time modification", which has the ability to reverse cause and effect and change the past. The major problem is that the practitioner needs to consider the size of the Bounded Field and the scope of time that needs to be modified. It requires a large amount of prana and similar rituals in the same magnitude of High-Thaumaturgy to activate it. It would normally be applied to a wide area and a long period of time, taking longer to set up and more prana to utilize it as the Bounded Field becomes larger and the deviation in time becomes longer.
It is not an ability that can be used on the battlefield where strategies must be quickly made in order to survive, as it must be prepared beforehand and used strategically even after the preparations. The Magic Crest of the Emiya family contains generations of inherited research, but that is unimportant to Kiritsugu. It was a useless inheritance until he found a way to use it to its maximum potential in a combat situation. He worked around the issue of size and prana consumption by creating a flexible method of utilizing it on a small scale that only applies to himself. This allows for the establishment of the Reality Marble at any given time without the need of extended rituals. It is impossible to completely isolate the flesh from the outside world, but the ability can minimize the effect the outside world has on the body. Keeping the scope of the spell to a minimal bounded field within his own body, it doesn't allow for the world to be affected, but rather allows for Kiritsugu to "adjust" a few seconds of time within his own body. He uses the chant Time alter (固有時制御, ?), followed by the degree of speed he wishes to use. The chant accel (速, ?) allows him to speed up, while stagnate (停滞, ?) slows him down. He can use Release alter (制御解除, ?) to stop it an any point.
Time alter - double accel (固有時制御二倍速, ?) is his most used version, allowing him to move faster than the human eye can see. It speeds up his blood flow, hemoglobin metabolism, and muscle movement all at the same time. Using this brief burst of speed, he can use his own physical skills and reaction speed at a level far above human limitations. It allows for split second evasion in front of an enemy, and its power of mobility can make for one of his greatest defenses. Normally double accel is enough to push his body past its limits with brief use, but with Avalon providing regeneration, he is capable of using Time alter - triple accel (固有時制御三倍速, ?) and the quadruple-accelerated time of Time alter - square accel (固有時制御四倍速, ?) for an extended period of time. Using stagnate, he can slow his biological processes, and using Time alter - triple stagnate (固有時制御三重停滞, ?) reduces them to one third of their normal speed, slowing his heart beat to the point where he can barely feel it himself, slowing his breathing so it lags, and reducing his metabolism to the point where body temperature cools quickly enough to almost match room temperature. The sound of his presence is reduced enough that Volumen Hydrargyrum is unable to make out his breathing and heart beat from the other noises in the natural world, and it is unable to recognize him by using the standards of a human. While there aren't any changes within the actual world, his optic nerves and ear drums register what he sees and hears from within the bounded field. His cornea receive three times the light a person's eyes normally receive, which makes his field of view extremely bright, and his hearing is dulled.
Even with his minimalistic approach, it is still High-Thaumaturgy far above the level of basic physical enchantment that causes inconsistencies between the flow of time inside and outside the field. Once the movement is complete and the field is removed, natural forces, the "world’s own adjustment", will forcefully adjust the "incorrect time." This places a large burden on Kiritsugu with each use, as the bounded field where the "errors have occurred" is within his own physical body. In order to get back in sync with the normal time flow, adjustments occurring within his flesh greatly damage him. Even brief use has him accompanying death, and continuous activation is nothing less than suicide, making it his riskiest technique. When returning to normal from stagnating, he suffer from the blood flow speeding up back to original speed, which causes burst capillaries and internal bleeding. Without the use of Avalon, double accel is his limit when speeding up, and even a few seconds of it is enough to rupture numerous blood vessels and cause fractures in the bones of his limbs due to the burden. Provided with constant regeneration from Avalon, he makes use of the ability's purpose as a strategic weapon to its full potential by utilizing higher levels while enduring his body breaking down and healing at an extremely high rate. He still feels the torn tendons and snapping bones tormenting his nerves while shedding mists of blood with every movement, but the regeneration allows him to keep fighting with accelerated speed for a much longer duration of time.
