A Signature in the Periphery - Part One

Thinking back on my experiences in the Artisan Camp always fills me with a bizarre feeling.
It's as if there was always something following me like a shadow, only appearing in the edges of my vision, and when I focused my eyes on it, it immediately dissipated into nothingness.
—During the artisans' experiments, it appeared on the wall being tested.
—During the clockwork chicken experiment, it even appeared inside the clockwork structure.
—When Priest Juster and the artisan leader, Valerian, were having their secret chat, it appeared on the leaves whipped up by the strong wind.

What on earth is it... In my memory, this thing also seems to have developed deviations, as if even it itself had started to succumb to the uncertainty.