This is one of those classic UFO lore documents. The German Wikipage is much more expansive in context, here's a short translated part that should tell you all you need to know about this one:
> Magin concludes by pointing out that reports of supposed “battles in the sky” were already very popular in antiquity and especially in the Middle Ages and were written down in astonishingly large numbers and distributed on leaflets and woodcuts. At this time, the Christian religion had a great influence on the everyday lives and world view of ordinary people and interpreted celestial phenomena of all kinds as “divine miraculous signs” or “warning signs from God”. Accordingly, the illustrations are littered with Christian symbols. Pious people saw themselves “admonished by God” through such leaflets and miracle reports to confess and remain faithful to him. A report such as Glaser's would therefore come as no surprise, as the people of his time would have known how to interpret the leaflet correctly.
> Magin concludes by pointing out that reports of supposed “battles in the sky” were already very popular in antiquity and especially in the Middle Ages and were written down in astonishingly large numbers and distributed on leaflets and woodcuts. At this time, the Christian religion had a great influence on the everyday lives and world view of ordinary people and interpreted celestial phenomena of all kinds as “divine miraculous signs” or “warning signs from God”. Accordingly, the illustrations are littered with Christian symbols. Pious people saw themselves “admonished by God” through such leaflets and miracle reports to confess and remain faithful to him. A report such as Glaser's would therefore come as no surprise, as the people of his time would have known how to interpret the leaflet correctly.