In the Fullness of Time
It's a late spring night with clear skies, warm and pleasant. The nearly full moon shines brightly over Arx. And then the shadow of something high, high above the city can be seen against the moon as it passes over. It's quick, it only takes about ten seconds at most. No one gets a good look at it. The general consensus from those who saw it is that it must have been a strangely shaped, fast moving cloud, although there were no other clouds in the sky. A few remark that the barely audible hissing was a bit weird.