These are artificial lifeforms created in order to allow the holy Grail War to proceed smoothly.
They may seem the same as NPCs because they are manufactured beings, but High Level AI have firmly defined liberties and personalities, and they also are bestowed with a soul.
Due to the high cost of manufacturing High Level AI, they are not reset even after a Holy Grail War has finished.
They make an appearance filling standard character roles in each Holy Grail War.
High Level AI include:
Father Kotomine, whose duty is to supervise the Masters.
Sakura, whose duty is to manage and maintain the Masters’ health.
Disciplinary Chairperson, who keeps an eye out for bad conduct within the school.
Ms. Taiga, who directs the schedule each day.
The mysterious black panther Makiji… and more.
The group of High Level AI also seems to include Sister Karen Caren, whose jurisdiction is carrying out the punishment of Masters, however she doesn’t seem to make an appearance in the Holy Grail War that the protagonist participated in.
Also, the memories that the High Level AI have obtained are unable to be deleted by themselves. No matter how sad and depressing a memory may be they are forced to keep it with them forever, and of course submitting their memories to Moon Cell is the reason that they exist.