“So, as for the reason I brought up an alliance... Last night, I spotted a monster in the city.”
“A monster?”
“I don’t know if you know them, but they’re called vampires, and they feed on humans’ life blood. They’re humanity’s natural enemy and the Holy Church’s sparring partners. Oh, first, do you know about the Holy Church?”
Saber started with the basics. The long-haired Heroic Spirit shook his head.
“Only the information I received from the Grail. There was not yet a Holy Church in my time. As for these bloodsucking monsters... I wonder. There were monsters that fed on flesh and blood, but I do not know if they were the same.”

Fate/Strange Fake: Volume 3, Chapter 8 ("Day 1, Afternoon")