Complex sentence: Literature mirrors cult practice, in which the appearance of blood rain was considered a bad omen, and was used as a tool foreshadowing events, but while some of these may be literary devices, some occurrences are historic.
Split into simpler sentences: Literature mirrors cult practice, in which the appearance of blood rain was considered a bad omen. It was used as a tool foreshadowing events, but while some of these may be literary devices, some occurrences are historic.