The Einzbern Family.
Descended from the wielder of the Third Magic, they were one of Fuyuki City's Three Founding Families.
They were also among the few families that commanded Magic. They had contributed considerably to the Holy Grail War, and the Lesser Holy Grail resided inside the Einzbern Family's Master.
Ever since the Third Holy Grail War, the Lesser Holy Grail had been placed inside an Einzbern Family homunculus, and this generation's Illyasviel von Einzbern possessed virtually the greatest number of Magic Circuits.
When Karn first arrived in this world, he had considered taking control of Illyasviel, the Lesser Holy Grail. But back then, Sakura Matou could not supply enough magical energy. Even if he joined forces with Rider, they might not have been a match for Heracles.
Once he had enough magical energy, Sakura Matou could also absorb Servants' souls, so Karn no longer needed to seek out Illyasviel.
When it came to absorbing Servants and returning them to the Holy Grail, the Holy Grail fragments inside Sakura Matou seemed to have more of an advantage.
"Sella, have you found out what happened in Fuyuki City?"
While eating breakfast, Illyasviel asked about the massive explosion in Fuyuki City some time ago. To this day, it remained an unsolved mystery.
Although Karn could erase the memories of Fuyuki City's high-ranking officials and some of its residents, there were too many people in the city for him to erase everyone's memories. He did not want to waste that much magical energy, either.
"My lady, we haven't found much useful information. What we can say for certain is that this was a battle between Servants, but few people saw what happened, and many seem to have had their memories erased."
Sella reported to Illyasviel. Only three people lived in this Einzbern Family