The absolute authority over Servants granted by the Holy Grail to magi (Masters) taking part in the Holy Grail War. Aside from giving Masters the power to order Servants to take certain action—whether they want to or not—up to three times, Command Spells can also be used to enhance a Servant's abilities or magical energy. Once a Master has exhausted or lost all of his/her Command Spells, he/she loses the right to participate in the Holy Grail War.
Special familiars summoned by Masters during Holy Grail Wars. Heroes worshipped in mythology and legends, they materialize in their past peak form, thanks to the power of the Holy Grail. One from each of the seven classes of Servants—Saber, Archer, Lancer, Rider, Caster, Assassin, and Berserker - is summoned, and each possesses a powerful Noble Phantasm. Servants comply with being summoned in order to have their own wishes granted, and it is for that purpose that they fight alongside their Masters.
THE HOLY GRAIL WAR
A ritual to bring about the descent of the Holy Grail, an omnipotent container capable of granting any wish to whomever claims it. Under the supervision of the Church and the Mage's Association, the seven Mages (Masters) summon seven Heroic Spirits (Servants), after which they engage in a battle royale until only one is left standing. Until now, four Holy Grail Wars have been waged in Fuyuki, and the scars left from those conflicts can be found in various locations.