When listening to amazarashi's song "つじつま合わせに生まれた僕等" on Youtube, the first "誦読" part has such a sentence "降らば降れと天をにらみつけ."
Intuitively, It sounds like a causative-conditional conjugation to me and means something like "if it befalls on us." But I'm not sure. Can anybody out there shed some light on it?
First of all, thanks @naruto for the reply. And after digging around for a while, I found 2 pieces of information that might also be useful to future readers of this post.
By the way, I like this tiny part of the info: