Cathedral (Bounded Field)
A phase-transforming, isolation-type bounded field developed to contain Rank Ⅸ Dead Apostles.

It originally belonged to the Ancestor signifying kingdom, and was a wall with a 30km diameter that isolated everything it enclosed from the outside world. Compared to the original, Ciel's version is a conceptual barrier that can only contain a single instance or kind of object.

On the other hand, it possesses a space distortion function that the original lacked, allowing the user to alter the size of the space within at will. As this High Thaumaturgy demands a special sort of magical energy to be used, it cannot easily be used repeatedly.

Tsukihime Material I - Cathedral (Bounded Field)