Holy Grail War

The War of the Holy Grail (聖杯戦争) is the competition that decides the ownership of the Grail through intense battle royale.

The war of the Fuyuki city is unique, as it is the only one that has a Servant system that uses Heroic Spirits as familiars. It is to be noted that the war of the Fuyuki city is apparently not the only "war of the Holy Grail", as there seems to be several artifacts labeled as the Holy Grail and different competitions for their ownership.

The Grail War of Fuyuki
It is the name of the competition for the ownership of the Grail between the magi chosen by the Grail, but it really is the ritual planned out to recover the Third Magic lost by the Einzberns, the "Cup of Heaven" (materialization of the soul). In Fate/stay night, this is the fifth war. Apparently, all five have occurred during Winter.

The English name is "Heaven's Feel (ヘブンズフィール)"; the first Holy Grail War is thus called the "Heaven's Feel 1", the second is "Heaven's Feel 2", etc.

Origin and purposes
It was created 200 years ago by three families, with Justizia Lizleihi von Einzbern, Tohsaka Nagato and Makiri Zouken, who were trying to create a gate leading to Akasha. At that time, the Mage's Association and the Church were locked in a fight to the death, so a land in the Far East, where the Church couldn't see, was chosen. Einzbern prepared the vessel for the Grail, Tohsaka called forth the Servants, and Makiri designed the Command Seals that command the Servants.

Currently, only the Tohsakas want to reach Akasha, while the Einzberns and Makiri only want the completion of the Grail, that is, the revival of the Third Magic. However, both Matou Zouken and Emiya Shirou note these goals seem to be impossible as there was never a victor for the past four Heaven's Feels and the Grail became corrupted by Angra Mainyu after the Third war.

Procedure
A cycle of 60 years is needed for the Great Grail to amass enough mana to summon the Servants. The time period between the fourth and fifth wars was the shortest - 10 years.

The participants are 7 Masters and their Servants. It appears as a battle royal that lasts until only one stands, but the real point is to fill the vessel of the Grail with the souls of the Servants. Defeated Servants turn back to being pure energy and should disappear from the timeline they are incarnated into, but the function Grail of the Einzberns is to stop that temporarily and collect them. Once the vessel is filled, the energy of the Heroic Spirits returning to the "Throne" is used by the Great Grail, in a ritual to open a "hole" leading to Akasha.

The Grail selects the magi who will summon the Servants, the Masters carrying three Command Spells to have the Servants obey them. The magi are then called Masters.

Involvement of the Church and the Mage's Association
For the positions of Masters, the Grail first favors magi from the three original families. Then it picks magi who earnestly want it. The Mage's Association has an interest in it.

Bazett Fraga McRemitz, a cleaner specialized in the "designations for sealing", was sent for the fifth war by the Mage's Association, as they had sealed the order of concealing the 726th Grail from the world of men, because of its potential to become the real one.

After the third war, it was agreed that the war was too dangerous to not be supervised. However, because of political implications, there is nobody in the Association that can be fit as a referee. For that reason, they had no choice but to have recourse to an external authority such as the Church.

It was proven long ago that the Grail of Fuyuki wasn't the one that received the blood of the son of God. Still, the Church sent a supervisor because it was too risky to ignore the huge power of the Grail of Fuyuki, but as they wanted to avoid any collision with the Mage's Association should they decide that it was a heresy to remove, they opted for the backup plan of entrusting the Grail to a person of their choice.

At the end of the third war, the then young Kotomine Risei was appointed to become supervisor, which he did for the fourth war. In the fifth war, his son Kotomine Kirei took over the position.

History
From the point of view of the Einzberns, the first time ended before the completion, the second pointed out flaws in the rules, they called Avenger the third time, and were betrayed by Emiya Kiritsugu the fourth time. Since the third Grail War, the Church started dispatching a supervisor. In the first and second, nobody that was "something other than a Heroic Spirit" was summoned (compared to the fifth war, where we have Caster and Rider). The Grail War turned wrong during the third installment.

At the end of the fourth Holy Grail War, Kotomine Kirei caused the large fire that killed 500 people and destroyed 134 buildings, and Emiya Kiritsugu destroyed the Grail.

It is suggested that the inconclusive termination of the 4th War -- the Grail's failure to grant a wish to the selected victor (Emiya Kiritsugu), and the victor's subsequent destruction of the grail -- resulted in the premature occurrence of the subsequent War. More specifically, the unexpended thaumaturgical energy accumulated through the elimination of Servants was recycled, permitting the Great Grail to reach the required threshold to launch the 5th War a mere decade later.

Following the 4th War, Emiya Kiritsugu arranged as an eventuality the physical collapse of the Great Grail System before the originally estimated date of the 5th War -- utilizing stocked dynamite and the manipulation of leylines to ensure a severe localized earthquake in the targeted area within 30 to 40 years of the 4th War. However, due to the premature occurrence of the 5th War, Kiritsugu's plan would only eliminate the 6th. Also, opposition of the Fuyuki Grail from the Magecraft Association resulted in the dismantlement of the system sometime in the late 2000's to early 2010's (sometime after the 5th Heaven's Feel) by Waver Velvet El-Melloi II. In the Heaven's Feel scenario, the Great Grail is either finally destroyed by Emiya Shirou (normal end) or closed down for good by Illyasviel von Einzbern (true end).

Thus, regardless of the route followed in Fate/stay night, the Fuyuki Grail Wars definitely ends with the 5th, and there is no Heaven's Feel 6.