Reality Marble

A Reality Marble (固有結界 koyuu kekkai, inherent/characteristic bounded field) is the commmon sense of the spirit world that the demons possess, but now, it is possible to achieve one as a characteristic bounded field.

As a sub-category of Marble Phantasm, it is possible to reshape reality into the vision of the bearer through a bounded field. It is a magecraft that comes close to being real magic, and is a category that was banned by the Association of Magecraft.

Unlike Marble Phantasm, it isn't possible to make any transformation you want: its only purpose is to do the one thing that defines the practitionner. On the other hand, that thing can be something unnatural.

The Reality Marble allows the creation of a world that obeys a set pattern of rules. However, there are limitations in how it is a way to create a spiritual world. In principle, it is something that only belongs to demons and spirits, but it is possible for an individual with high magic abilities to realize one with time. The World will naturally try to crush such a bounded field if it isn't made by a spiritual entity. Also, in the end, only a limited number of people are capable of realizing a Reality Marble.

The majority of the 27 Ancestors seem to be capable of realizing one. By the way, Nero's own body is a Reality Marble, so that the World will not try to crush it. Well done, Professor Nero.

List of known Reality Marbles and their owner:
 * Depletion Garden (Yumizuka Satsuki)
 * Lair of the Beast King (Nrvnqsr Chaos)
 * Nevermore (Grandsurg Blackmore)
 * Night on the Blood Liar (Zepia Eltnam Oberon, AKA Night of Wallachia)
 * Overload (Mihail Roa Valdamjong)
 * Parade (Fina-Blood Svelten)
 * Unlimited Blade Works (Emiya Shirou, Archer)

Brunestud of the Crimson Moon also had a Reality Marble that created the Millenium Castle. This Reality Marble can be inherited, and Arcueid can recreate the Castle through her Marble Phantasm, a feat that granted her the name of Brunestud.

Ionian Hetairoi, "the Army of the King", Noble Phantasm of Alexander the Great, is a variation of a Reality Marble, as it is a combined Reality Marble of Alexander and his whole army.

The ability Innate Time Control of Emiya Kiritsugu also seems to be close to qualify as a localized Reality Marble (like Nero's).