Cathedral (Bounded Field)

A phase transition-style, isolation-type Bounded Field developed to contain IX-rank Dead Apostles.
It is something that was originally possessed by an Ancestor who represented Kingdom, and it isolates the interior from the outside world surrounding it with a wall of diameter thirty kilometers, but unlike the original, Ciel’s has become a conceptual barrier that can contain one unit or one kind of an object.
On the other hand, it is equipped with a spatial distortion feature that the original doesn’t have, and it is possible to alter the size of the space within arbitrarily. Since a special mana is required for the employment of this High-Thaumaturgy, it cannot be fired successively with ease.

Tsukihime Material I: Tsukihime Work Glossary