Mystery

is a sliver of power of many different types that comes from the Root.
It is the source of all supernatural phenomena such as magecraft or ESP, and beings such as True Ancestors, Dead Apostles, Servants, Spirits, as well as Phantasmal Species show signs of Mystery. Mystery accumulates over time and grows stronger with age.
==Overview==
The word 'mystery' derives its etymology from the Greek mystêrion, the root of which, myo, means "to close or shut", and can be understood variously as shutting, concealing, and self-completion.Kara no Kyoukai Volume 5: Paradox Spiral (Enjoh Tomoe) - /6Mahoutsukai no Yoru - Chapter 6: "Like a Dog"Lord El-Melloi II Case Files Volume 1: case. Adra Castle Separation - Chapter 2 Part 3 A Mystery thus holds meaning specifically because it is a mystery; if it were to be understood, it would lose that force.Lord El-Melloi II Case Files Volume 1: case. Adra Castle Separation - Chapter 4 Part 1
Magecraft is, in essence, Mystery. However, since the beginning of the Common Era, human history has been in the process of systematically erasing Mysteries. As the light of science expands, the darkness of Mystery recedes, and humanity has reached the point where everything is explainable with human knowledge, from the workings of nature to the operation of the cosmos that was once the purview of the heavens, anything that was once beyond the ken of man. No matter how magi resist this fact, this law remains unbent. The Mysteries of the Age of Gods have become so distant that even realizing them temporarily in the modern world is next to impossible.Lord El-Melloi II Case Files Volume 1: case. Adra Castle Separation - Chapter 1 Part 2 The decline of Mystery has been accelerating since the death of Solomon, the King of Magecraft, before the Age of Gods came to an end at the start of the Common Era.Garden of Avalon - Chapter 02: The Light of the Stars
This greatly affects magecraft. A magecraft that has had its nature revealed can't become a Mystery, no matter what kind of supernatural methods it uses. It's now nothing more than another mundane method. For example, Automatons have become a lost art in magecraft and the concept of homunculus creation is steeply in decline because, as knowledge of the human body deepened and spread throughout humanity, to the point humanity accepted that there were no Mysteries to be found within their own bodies, they had lost the grounds to be fields of magecraft. Even if one accepted the theory that the human body still is a black box, and the Mystery within it was not yet entirely erased, the fact that modern magi in the field can't compare to even antiques from hundreds of years ago is an undeniable fact.Lord El-Melloi II Case Files Volume 2: case. Twin Towers of Iselma (Upper) - Chapter 3 Part 4 
Magecraft thus gets weaker when it's exposed, though what is meant by that is not the magecraft of a particular individual, but all of magecraft and in the future, not the present. Paradoxically, despite losing its power when propagated, a Mystery becomes more stable as knowledge about them spreads thanks to the system of Thaumaturgical Foundations. Engraved into the World, its strength can be greatly influenced by the faith and the collective unconscious of the people.
== Concealment of Mystery ==
In order to stave off the degradation of Mystery, the Mage's Association was founded, and it began enforcing the to preserve the strength of magecraft. It was previously something of an unwritten law, but became enforced over time, with the popularization and vulgarization of Mysteries being tantamount to a crime in the World of Magecraft. In fact, in the past, magi could even make a career of magecraft and be recognized by society, so long as they kept the details of their individual magecraft a secret they would take to the grave, but now it has to all be kept under wraps. The Association feared that if they did not go that far, magecraft in the distant future would be reduced to nothing more than another product to be consumed and thrown away. 
The Mage's Association’s policy of entirely concealing the existence of magecraft was established during the , likely some time in the early 1200s, as the reign of Richard I was the last in the age when such things were out in the open.Fate/strange Fake Volume 3 - Chapter 8: Day 1, Afternoon (2) "The Wandering King's Rock'n'Roll" Other organizations in the World of Magecraft generally obey this rule, though the Holy Church have been known to openly flout the policy in regards to their Baptism Rites.Lord El-Melloi II Case Files Volume 7: case. Atlas Contract (Lower) - Chapter 3 Part 3 The magecraft organization controlled by the United States government is the most extreme exception, being outright hostile to the idea of concealing magecraft, and as such are labeled a “scourge” to Mystery by the Mage's Association.
In the World of Fate/strange Fake, Lord El-Melloi II estimates that the Concealment of Mystery won't last more than another five years, as they approach a time when anyone can upload high definition images to social networks in real time,Fate/strange Fake Volume 2 - Chapter 6: Day 1, Noon "Two Archers and..." notably thanks to smartphones.Fate/strange Fake Volume 5 - Bridge Chapter: "Rondo of the Outsiders" Once that happens, the ability of information to spread will outstrip the pressure to conceal it. As the danger of Mystery being recorded increases, either new methods of secrecy will have to be devised, like seeding dummy stories and label everything , or they will have to reveal something. 
In some possible futures, the Concealment of Mystery has partially or entirely ceased, such as the World of Fate/Requiem, in which the knowledge and use of magecraft is commonplace among the public and the Mage’s Association only holds nominal authority over its secrecy,Fate/Requiem Volume 1: The Boy Among the Stars - Chapter 3 or the World of Tsuki no Sango, in which Spiritron-based technology serves as the power source for humanity’s Seven Lunar Cities. While contrary to the Mage's Association’s fears, magecraft has not ceased to exist in either of these scenarios, the "degenerated" condition of humanity in Tsuki no Sango may have caused it to diminish.
Mystery hasn't degraded everywhere however. Compared to the surface, the Texture of the Human Order influences the underground much less, so traces of Mystery still remain in the depths of the Earth. For that reason, there will be fragments of things that have disappeared aboveground there, like pieces of Phantasmal Species.Lord El-Melloi II's Case Files Volume 8: case. Grand Roll (Upper) - Chapter 2 Part 4 Islands as well, due to being isolated from the mainland, have had Mysteries from the Age of Gods remain longer,The Adventures of Lord El-Melloi II Volume 3: The Devil of the Wandering Sea (Lower) - Chapter 3 such as Britain, the "navel" of the planet, and Japan, whose Age of Gods outlasted Britain's. Continents are firmly part of the human world, thus, as countries are connected by land, the rewriting of the physical laws proceeded quickly.
If two different types of Mysteries collide with one another, the stronger Mystery will overwhelm the weaker one. It is through this law that Lugh Beowulf is able to remain invincible against modern magecraft; because he has 3,000 years' worth of Mystery, which is far more than any modern magecraft has, he is able to simply ignore any effects that magecraft would have on him.Mahoutsukai no Yoru - Chapter 12: "Witch on the Holy Night II" Another similar case is Wuzhiqi, who is a Xian and thusly there are not a lot of Spells that can affect her in the modern world.The Adventures of Lord El-Melloi II Volume 1: The Man Who Devoured God - Chapter 4
== Thaumaturgical Applications ==
Time being of exceedingly high value in thaumaturgical applications, a Mystery strengthens the longer it has existed. For example, a family's Magic Crest becomes strong by having new accomplishments added to it by every generation to have received it. With a eight-hundred-year-old parchment, one may forge a Golem that can easily destroy one or two experienced magi.Fate/Apocrypha Volume 1: Apocrypha: Great Holy Grail War - Chapter 2 Likewise, certain items that have a long history and age can also show signs of Mystery, as in the case of the centuries-old katana that the Ryougi possess, Kanesada Kuji. If they are severely damaged, however, they will lose all the Mystery they have accumulated. 
Just as a jewel carried by many different people over a long time begins to be stained with their thoughts, making it easier to use in Jewel Magecraft, a tool bearing the feelings of many people would also begin to develop its own kind of Mystery. While for most objects that Mystery stays concealed forever, in some rare cases it can bloom forth, like the of Japan.Lord El-Melloi II Case Files Volume 2: case. Twin Towers of Iselma (Upper) - Chapter 4 Part 3
It is also possible for a human's body to reach the level of a Mystery, such as with Shiki Ryougi. There are also the cases of Doctor Heartless, a magus who got his heart stolen by fairies,Lord El-Melloi II Case Files Volume 5: case. Mystic Eyes collection train (Lower) - Chapter 5 Part 1 and the Mixed-Blood Kouma Kishima (Remake), a true Crimson Red Vermillion, who have both become a Mystery.
With Rhongomyniad Mythos, Gray can contain Mystery and make sure none of it leaks outside, such as using it to keep the power of Typhon contained in Bai Ruolong so he cannot use its abilities.The Adventures of Lord El-Melloi II Volume 3: The Devil of the Wandering Sea (Lower) - Chapter 6 This is the true function that Rhongomyniad was made for, the ability to anchor the world in place.
==References==
it:Mistero
vi:Thần Bí
Category:Magecraft terminology
Category:Terminology in Fate
Category:Terminology in Tsukihime
Category:Metaphysics
Category:Terminology in Kara no Kyoukai
Category:Terminology in Mahoutsukai no Yoru
Category:Terminology in Tsukihime Remake