I even saw it once, at least I think so. Its shape was indistinct in that it was impossible to look at. As soon as it came under your direct gaze it would disappear, and therefore could only be glimpsed in peripheral vision. It moved, seemingly flying or hovering, slowly, yet with definite purpose. One could never be certain of its material existence, although its appearance was that of something corporeal, almost organic, yet with the callous functionality of an engine. Light was reflected from it, which suggests it has material form even if only the finest membrane. Although I can only claim one encounter, they say that it can often be seen, when it is near dark, or against a backdrop of intense bright light. It invokes both anxiety and nostalgia, and though instinct tells you it is not meant to exist, not here at least, we need it.