The Blood Moon Phenomenon. It was incredibly rare for it to occur, but it was indeed natural. Atlas knew about it as well, since it was something that took place anywhere under the Heavenly Law.
It was a rare natural disaster that occurred when the levels of a world's blood qi reached a certain point. It was supposed to be impossible to achieve in a neutral zone due to the conditions, but here it was.
The Blood Moon Phenomenon had different effects on different races. Demons under the High Demon rank were driven rabid by its light. Divine Beasts and other bestial species were weakened severely.
Humans were not particularly affected in either direction, however, their minds were altered and it was possible for them to either benefit from or be harmed by the phenomenon depending on their actions.
