Servants vs the sort of Boundary Field Kayneth set up during the 4th Grail War.
“Then, the Einzbern homunculus and Miss Borzak are helpless?”
“Not at all,” Faldeus immediately contradicted his subordinate as if his earlier praise of the workshop had been a lie.
“It would be one thing if they’d gone in alone. With the Heroic Spirit Haruri summoned, however, it’s a different story. The workshop in Fuyuki I mentioned was destroyed along with the entire hotel, but if a Servant well-versed in magecraft had challenged the labyrinth, they would have broken through it sooner or later.”
Faldeus’ opinion on this matter was the opposite of what it had been ten years earlier. A modern labyinthized workshop was difficult to penetrate; even a Heroic Spirit would need to exploit a weak point or back door, he had thought. Now that he had accessed the data from the puppet his ancestor had left behind — the record of the third Fuyuki Holy Grail War — and had contact with the Heroic Spirit Hassan-I Sabbah, however, he was in no doubt. A maze of that level would not work on a powerful Heroic Spirit.
Although I doubt that weak Avenger in the record of the third Fuyuki war could do anything about it, Faldeus thought as he turned his attention to a monitor.
“In any case, if she summons her Servant to break out of the workshop, it will be a golden opportunity for us to observe its abilities.”