TMdict

Formally called Moon Cell Automaton.
It is the energy storage device discovered within the Moon.
It is an artifact made by some non-human intelligent lifeforms, and is the super computer used as the setting for Fate/EXTRA.
There are seven layers confirmed so far in its cyber world structure. The first layer, which is the surface of the Moon, is accessible even to run-of-the-mill hackers.
To intrude into the second layer or deeper into the Moon is probably too difficult for non-wizards… or perhaps I should say that there is just no physical way to do so.
Transference of the soul — a body transformed into spiritrons, is necessary to be able to peek any further into the abyss.
Old world magi could connect with the interior portions of Moon Cell as part of meditation without using radio waves.
To put it simply Moon Cell is, “The eye that observes the Earth.”
Moon Cell is a computational device that accurately simulates all of Earth and its life forms, and can even accurately predict the future.
Moon Cell is a database of humanity. A colossal memory device that has recorded mankind’s ecology and history, and even the thoughts and souls of [all] people.
A Pandora’s Box that promises the next stage of evolution, promises god-like power to those intelligent lifeforms who have become technologically advanced enough to scan the interior of the moon.

Originally Moon Cell was just an observation device made by an otherworldly civilization.
Moon Cell only contained equipment to observe and record life on Earth, but after many, many years it came to have its current functionality.
Its mission was to observe, but when trying to observe there can be no “blind spots.”
(Heisenberg’s Uncertainty Principle. The observer determines an event by observing it. What isn’t observed is not certain.)
An observation device must be fair. If it is to observe, there must be nothing unseen. Thus, it required capabilities for knowing everything about the Earth.
To record all things without bias, it needed performance greater than that of an observation device.
And so, it had made a giant leap in evolution.
It had enhanced its functions to the point where it went from making observations to surveilling, even gaining control over the administration of the planet.

The greater its enhancements, the more complex its administration policy. It created many terminals and even made artificial intelligences to manage functions for each section. (These were later utilized for the NPCs and advanced AIs of the Holy Grail War.)
However, on the other hand, Moon Cell was stubbornly opposed to loading artificial intelligence into itself.
A true observer should not have a mind.
If an observer has an intellect and knowledge, the meaning of things observed will be decided by the observer.
For that reason, it kept to maintaining its absolute objectivity as an eye, doing so while always dismantling the emerging semblances of sapience that it had incorporated to administrate its functions.
Thus, this computer has no conception of good and evil, no desire for the future, not even an outcome.
Moon Cell is just a container that exists on the Moon.
A typewriter that God left behind.
An observation lens drilled into the Moon.

In the future, when looking back on this crystal device that just shows people dreams, Moon Cell will be called thus.
The Moon’s Eye.
A bottomless Klein Cube.
The observer of everything on our planet, and a Type-Moon whose master is no longer around.

Official Name: Moon Cell Automaton
An energy-storing body discovered inside the Moon.
An artifact constructed by non-human intelligent life.
The supercomputer that serves as the stage for Fate/EXTELLA.
Up to seven levels have been structurally identified in cyberspace, and the first level, the surface of the Moon, is accessible by even normal hackers.
However, going beyond the second level is difficult for anyone other than Wizards. In fact, there is no way to physically invade the Moon past this layer
Without soul transference into a digitized body converted into virtual spiritrons, it is impossible to gaze into its abyss.
However, it is said that the ancient practitioners of magecraft could make contact with the inside of the Moon Cell simply by meditating, instead of using electric waves.
The Moon Cell is, in essence, “an eye that observes the Earth.”
A processor with a massive memory that has recorded the habit, ideas, and even the souls of humanity, it acts as a database of human history and faithfully simulates all life on Earth.
It can be thought of as a Pandora’s Box that will usher in the next stage of evolutionary growth, promising god-like power to the intelligent life forms who become technologically advanced enough to access the Moon’s interior levels.

Originally an observation device left behind by an alien civilization.
It was at first only capable of recording the nature of life on Earth, but after many years, it came to possess its current abilities.
To properly fulfill its role as an observer, the Moon Cell determined that there must be “nothing left unseen.”
(This action was derived from Heisenberg’s Uncertainty Principle, which states that the observer determines an event by observing it, while that which is not observed cannot be certain.)
By its very nature, an observation device must be impartial. Thus, in order to record all things without bias, the Moon Cell required virtual omniscience, and focused its self-development toward that end.
It enhanced its functions beyond mere observation into a colossal computation device capable of conducting active surveillance and understanding the inner workings of the planet.

These greater enhancements caused its administration policy to become more complicated, with many terminals and even artificial intelligences created to assist in managing the functions of each section. (These were later utilized by the NPCs and advanced Als in the Holy Grail War.)
Despite these advances, the Moon Cell firmly held off on installing an artificial intelligence for itself, in order to maintain its commitment to absolute objectivity.
To remain impartial, the observer must not have a mind, for a mind would result in meaning being attached to the events being viewed.
And so the Moon Cell remained an impartial observer engaged in purely functional activities, continually removing any semblance of “intelligent” functions arising as it worked.
It was a computer with no conception of good or evil, no desire for the future, and no interest in any outcome, it simply observes, a “typewriter left behind by God,” as one researcher put it.

It is worth noting that the Holy Grail Wars did slightly change the nature of the Moon Cell, via events that were held for the purpose of recording the activity of the human mind, as well as through the choices of the War’s victor, the Main Character.
In the future, SE.RA.PH is likely to transition from a strictly observational platform to a stage upon which humanity will evolve.
For now, the Moon Cell continues to record history
Its function as a machine that simply provides the world remaining unchanged.