“A magic square! But it was impossible to detect it!” (Burkhart)
There are many traps, using magic spells, existing in the historic ruins from the time of the Ancient Magic Civilization.
Naturally we were taught about a majority of them in the lessons at the prep school. If it was a trap using normal magic spells, it might be possible for a magicians, having a certain degree of competency, to detect it.
“Tsk, we were careless!” (Burkhart)
“Burkhart-san! I can’t move my feet!” (Wendelin)