Ruler (ルーラー, Rūrā?), Heroic Spirit of Arbitration (裁定者の英霊?), is a non-standard Servant Class brought forth for the purpose of presiding over Holy Grail Wars. The Fuyuki Grail utilizes its own logic to sense when actions are encroaching upon its authority, and regardless of other mediators like those from the Church, it brings forth Ruler to protect the concept of the Holy Grail War itself. In the case of the reserve system of the Greater Grail being activated in the Great Holy Grail War, Ruler takes neither side of the battle, but only acts in the interest of the Grail. The Ruler-class Servants are given Command Spells for the other Servants.
A Ruler is also summoned to preserve the laws of Heroic Spirits to ensure they won't be violated, such as the law of "the dead not leading the living", touted as the greatest law of Heroic Spirits,  and to maintain human history by preserving the illusion behind the Age of Gods so that people do not know about the truth behind it. The role of a Ruler is to arbitrate the truth and adjudicate all things in order to maintain human history.
The criteria to be summoned for the Ruler Class is impartiality and possessing no desire for the Holy Grail. Those who qualify are most often Saints, and any Ruler summoned to preside over a Holy Grail will be a Saint under normal conditions. Within other systems like the FATE System, others who meet the criteria can be summoned. One exception to the normal rule of impartiality is Amakusa Shirou Tokisada, an aberration who does not normally qualify, summoned by the Einzberns as the Heroic Spirit who was considered the closest to a ‘Saint’ that could possibly be found in the Far East.
- Servants marked with ‡ are also able to be summoned by Ritsuka Fujimaru in the Grand Orders.
- Servants marked with ⁜ are those who change class mid-story but do not display characteristics substantially different from the original class.
Rulers with modified Saint Graphs
Servants possessing the Class of Ruler through the modification of their Saint Graph rather than a standard summoning.
Non-Servant beings with the Saint Graph Designation of Ruler.
Other qualifying heroes
|True Name||Current Class||Notes|
|Robert E. Lee||None|||
- Fate/Apocrypha Volume 3: Triumphal Return of the Saint - Chapter 4
- Fate/Apocrypha Manga - Chapter 47: "Maria the Ripper"
- Fate/Apocrypha Anime - Episode 13: "The Last Master"
- Fate/Grand Order - Sherlock Holmes' Trial Quest summary, translated by taiboo at Reddit.
- Fate/Apocrypha Volume 2: Round Dance of Black / Festival of Red - Chapter 3
- Fate/Grand Order Chaldea Ace