Back on Earth, Lex had encountered, and even studied many religions. It wasn't because he was particularly faithful, but because when he was young mobile phones didn't exist yet so he had to entertain himself in other ways. That would, naturally, include reading the books that lay around the house when it wasn't possible to go outdoors.
A common theme, he discovered, among many faiths was the end of days. Raining fire, ground shattering earthquakes and locust plagues were also very common in them, which is why Lex began to wonder if the Hollow was using his own memories as a template for the retribution.
He wouldn't say it was unoriginal. Why did that matter? As long as it worked, it would be good enough. It was just that, despite the fact that all of this was actually quite powerful and was affecting the necklace's body, the danger didn't scale properly.
