But it wouldn't have affected the humans, I take it? From where could such a thing originate? If no individual is responsible for it, yet it is coming from the war?

The only thing I can think of is that they would need to have some sort of common interest or goal that fighting a war would interfere with. But I'm still working on it...

(Side question that will need to be addressed at some point, but can be added to the list: Do humans have any sort of magic at all? Would witches and wizards and warlocks be part of the supernatural population? Do those even exist?)