Members of the church are tasked with watching over the Fuyuki Holy Grail Wars. After the Third Holy Grail War, the Mage's Association agreed to let the church supervise due to the artifact being fought over being called the Holy Grail.
- Risei Kotomine - Third and Fourth Holy Grail Wars
- Kirei Kotomine - Fourth and Fifth Holy Grail Wars
- Shirou Kotomine - Great Holy Grail War (Not officially recognized by all parties, chosen by the Association to maintain good relation with the church)
- Hansa Cervantes - True and False Holy Grail Wars (Not officially recognized by the participants, sent by the church of their own accord).
If a Ruler-class Servant is summoned by a Grail, they will be sanctioned to watch over the Holy Grail War.
SE.RA.PH watches over the Moon Holy Grail War and appoints AIs and NPCs as necessary. It will also delete those who break the rules, but it is possible for some Servants to fool it or avoid detection. Kirei Kotomine is designated as a Supervisor who deals with Masters. Archimedes is tasked by SE.RA.PH to take charge of its security. Within the Sakura Labyrinth, BB takes on the self-appointed role of "Gamemaster" and has almost complete control of the area.