Though she looked down on the happenings outside, what was reflected in her eyes
was not the view from the nearby window.
A magus' servant. Depending on the school of magecraft, they were called things like
Familiars or Agathions, or as in the Far East, Shikigami. Touko was of course using a
puppet. Having taken an interest in the rumors of a certain magus using wires to create
Familiars in the Fourth Holy Grail War, she had made a puppet out of springs, gears,
and string herself.
Though looking at it now, it didn't seem like something that could be described as
having been built on such a flimsy whim. For Touko, creating a puppet that served only
a single function with no other features was, simply put, boring.
Wings were lined in brass, eyes formed of rubies, that Familiar was soaring above the
tower twin to the one Touko now occupied.

The Case Files of Lord El-Melloi II, Volume 3, Chapter 1, Part 5