|Character type:||Servant (Master: None)|
Ruler (ルーラー, ?) 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. According to Joan of Arc, one of the criteria to be summoned for the Ruler-class is possessing no desire for the Holy Grail; the only exception to this was Amakusa Shirou Tokisada, who had a wish, due to how he was only Heroic Spirit who was considered the closest to a ‘Saint’ that could possibly be found in the Far East, where the Third Holy Grail War took place. The Ruler-class Servants are given Command Spells for the other Servants.
|Amakusa Shirou Tokisada‡||Third Holy Grail War||Einzbern Master|
|Joan of Arc‡||Great Holy Grail War||None|
|Joan of Arc (Alter)||Grand Order||None|
Servants possessing the class of Ruler for special reasons unrelated to a proper summoning.
|Saint Martha (Swimsuit)||Grand Order||None|