The concept of a Reality Marble (固有結界, koyuu kekkai^?, lit. innate bounded field) is having one's inner world materialized and projected onto reality following the World Egg (世界卵, Sekai tamago^?) theory. Generally, it is used to refer to the alien common sense of demons (悪魔の持つ異界常識, akuma no motsu ikai joushiki^?) in that it is how demons perceive reality and how Reality Marbles themselves are the natural abilities of demons and elementals. It is possible for humans to achieve this as an innate Bounded Field, though generally only in the cases of the powerful beings like The Twenty-seven Dead Apostle Ancestors and the greatest of magi who have spent years upon years researching. This ability is a similar and dissimilar method of "world creation" to Marble Phantasm, but rather than reshaping the world at their will, Reality Marbles allows only for the creation of a set world that defines the practitioner. They force all things to obey their rules, but it is limited only to that one pattern. It can be said that they can surpass Marble Phantasms at the same time, as they are capable of affecting things not of nature.^[1]

It is a magecraft that comes close to being real magic, and as a taboo among taboos and mystery among mysteries, it is one of the pinnacles for a magus for which research has has been banned by the Mage's Association.^[2] Those that do have a Reality Marble would inevitably earn a Sealing Designation if discovered due to its nature as a unique magical ability that cannot be acquired through study and does not pass on to one's descendants.^[3] Obtaining a Reality Marble is not something every magus can achieve through research. Caster, far above all modern magi, cannot utilize one, but she could construct "another world" of the same scale with enough time and expenses.^[4] Areas that are full of grudges, filled with remnants of strong regrets, are like Reality Marbles to spirits.^[5]

The created worlds are completely cut off from normal reality, projecting their internal landscape and sealing off the regular World. Following the World Egg theory, the actualization of a Reality Marble is the result of switching the Self and the World while keeping the boundary the same. The size of the Self and the World is switched, enclosing the World in a small container while the Self is expanded. The contained World is the World Egg and the name of the theory. They will encase anyone within range, causing them to disappear from view. Magi are still able to feel the presence of the Bounded Field, and while they cannot be directly affected from the outside, a large burst of mana, such as Excalibur, may be able to disrupt them. The World constantly attempts to crush the unnatural bounded fields, as they are not created by spiritual beings, meaning that it costs a great deal of magical energy to construct one and keep it stabilized. This generally only allows them to be used for a few minutes, but given their powerful nature, that is likely enough time to properly utilize them. Each world has its own set of patterns and rules, which can be said to be an invasion of reality by the diagram inscribed on the soul, and as it is just one aspect put into form, the user cannot add their own will into the form of the barrier.^[6]

In the case of Servants utilizing Reality Marble, it will generally be limited to the Caster class due to the spell's nature as high thaumaturgy, but there are exceptions like Rider.^[7] Those of the Berserker class will likely never be able to utilize them, meaning that most who use them will be powerful magi with low combat abilities.^[8][9] It is possible for practitioners to make use of certain aspects of their Reality Marbles without activating them. Unlimited Blade Works is the responsible for the Projection and Reinforcement abilities of its practitioners, and Rider is able to summon a single soldier from Ionioi Hetairoi at any time without bringing about the corrective impulses of the World. Some can be activated inside the body of the user, such as Unlimited Blade Works going out of control and creating swords inside of Shirou Emiya, and in a special case, Nrvnqsr Chaos only deploys his Reality Marble inside his own body, which allows him to avoid the corrective impulses of the World.

List of Reality MarblesEdit

• Aestus Domus Aurea (Ability similar to a Reality Marble used by Saber)
• Black Land (Part of Arcueid's Marble Phantasm extracted and made into a World Egg by Dust of Osiris)
• Crimson Moon's Reality Marble
• Crystal Valley (Ability similar to a Reality Marble used by ORT to passively transform the area around it into an alien crystalline substance.)
• Dead End Catharsis (Gen Urobuchi)
• Depletion Garden (Satsuki Yumizuka)
• Einnashe's Reality Marble
• Guru Guru Hisui World (Fake Reality Marble created by Hisui while under the effects of the Reality Marble of Night of Wallachia in Melty Blood)
• Hounouden Rokujyuyonshou (Bounded Field that is not a Reality Marble, but rather something that can be called an embodiment of Souren Araya's internal world)
• Ionioi Hetairoi (Irregular Reality Marble created from the shared wills of Rider and his entire army)
• Lair of the Beast King (Nrvnqsr Chaos and Maiko Yamase)
• La Pucelle (Joan of Arc)
• Nameless Forest (Caster)
• Neverland Overdrive (Kinoko Nasu)
• Nevermore (Gransurg Blackmore)
• Overload (Michael Roa Valdamjong)
• Parade (Fina-blood Svelten)
• Serial Phantasm, more frequently referred to as SE.RA.PH (System of the Moon Cell that generates a number of different Reality Marbles to function as the basis for the Holy Grail War of Fate/Extra)
• Field of True Summer Snow (Area generated by White Len that is similar in nature to a Reality Marble)
• TATARI (Night of Wallachia and Dust of Osiris)
• Time Manipulation (Concept with properties similar to a Reality Marble used by the Emiya family and Kiritsugu Emiya)
• The Queen's Glass Game (Relic allowing for the formation of Caster, a Reality Marble and pseudo-Servant based off the dreams of its Master)
• Unlimited Blade Works (Shirou Emiya and Archer)

ReferencesEdit

1. ↑ A similar and disimilar method of "world creation" as that of Marble Phantasms. Reality Marbles can force all things to obey their rules. Unlike Marble Phantasms, it is limited to one pattern. As just one aspect is put into form, the user cannot add his own will into the form of the barrier. On the other hand, as it can affect things that are not of nature, it can be said to surpass Marble Phantasms.
2. ↑ Reality Marble (固有結界) dictionary entry:
   最も魔法に近い魔術。禁忌の中の禁忌、奥義の中の奥義。魔術師にとっての到達点の一つ。
   A Magecraft close to Sorcery. A taboo among taboos, a mystery among mysteries. One of the pinnacles for a magus.
3. ↑ Sealing Designation (封印指定) entry:
   「学問では修得できない魔術、その体質のみが可能にする一代限り」
   A magecraft that cannot be acquired through study, the genetic makeup of which limits its practice to a single generation.
4. ↑ Q. Although it did not appear in the works, can Caster use a Reality Marble?
   A. Unfortunately, Caster cannot use it. But, if it is a magus of her level of excellence, by precisely constructing small magecraft and large magecraft, she can construct "another world" of the same scale, don't you agree? Well, the time and expenses required for that is vast, after all.
   (Q. 作中では出てきませんでしたが、キャスターは固有結界を使えますか？
   A.残念ながら使えません。が、彼女ほど超絶した魔術師なら、小さな魔術と大きな魔術を緻密に構築していく 事で同規模の「異界」を作り上げられるでしょう。まあ、その為にかかる時間と費用はやっぱり莫大なものです が。)
5. ↑ Fate/stay night Prologue - Day 2
6. ↑ Tsukihime Dokuhon PlusPeriod dictionary entry (p.179)
7. ↑ Fate/Zero - “How could this be….you could materialize the environment inside your mind…You aren’t a – magus?!” “Of course I’m not. This is not something I can do alone.”
8. ↑ Fate/Extra - Touko - "A Berserker? Are you sure you aren't mistaken? This Servant is using a large-scale reality marble, right? That's not a Berserker's style. A reality marble is highly advanced thaumaturgy. So if you think about it, a Caster makes more sense. …I'm sure there's more to the story, though."
9. ↑ Fate/Extra - Female Student: If you're talking about reality marbles, you won't see that many Servants using them. That Servant must be powerful to use a reality marble. The Master too, for that matter.