The characteristic feature of Rune Magecraft was these symbols. While it took time to
engrave them in the first place, once they were done, they could be released as a Single
Action spell by simply passing magical energy through them. The time lag between
activating the spell and its completion was vanishingly small. While that made the
effects that could be drawn out of them limited, it left no room for Flat to intervene.
...no.
Of course, that was hardly the first time Flat had seen a Single Action spell. At the Clock
Tower, those could be witnessed any number of times. And the Rune Magecraft itself
was something Touko had sold to the Clock Tower too, becoming widespread enough
that even Flat was capable of using it.
The problem was the beauty of her weaving.
Beyond obvious things such as with the Princesses of Gold and Silver, the composition
of a spell had an element of aesthetic beauty to other magi. In the same way a
programmer might admire another's code, the way she was connected to her magical
foundation was just too ideal.
It was a dream anyone who had dabbled in magecraft had no doubt entertained at
some point.
Her raw magical energy was not particularly overwhelming. Neither was she using
some sort of terrifying Mystic Code, as high-ranking members of the Clock Tower were
often wont to do. But the way her magical energy flowed had an air of perfected beauty
to it, as if flowing through a Möbius Strip. To Flat, who was more sensitive to the
magical energy of others than average, the aesthetic quality of it was even more
staggering.
So this is the ability of one who brought an entire field of magecraft - no, possibly more
than one, back from ruin.
And by simply witnessing that, Flat's mind was made up in an instant.
"Right, we've got no chance against her. Le Chien, let's get out of here!"

The Case Files of Lord El-Melloi II, Volume 3, Chapter 2, Part 3