During the Reformation, Luther and his followers looked for terrestrial and celestial portents, interpreting them as apocalyptic omens. The fiery appearance of aurorae lighting up the night sky made them especially suitable as signs of the end of the world. Although natural explanations existed for the causes of such celestial phenomena, moralistic writers preferred to see aurorae as admonitions of divine wrath in their literature of the last days. Korean historical records confirm that there actually was an increase in the number of aurorae seen in the mid-sixteenth century. This proliferation of aurorae, combined with the dissemination of printed accounts of their appearances, made these celestial wonders seem more quotidian than extraordinary. Ironically, the same evangelical authors who cited aurorae as ominous warnings simultaneously helped them seem less significant by drawing attention to how commonplace they had become in recent years. Rather than being naturalized, aurorae became ordinary.