My main trouble with our villain was that "nobody's listening to me" is kind of a pathetic motivation to kill people. Given her currently established personality, she's more likely to try and build up individual people than raise a death-army. So something isn't lining up.

What if, perhaps, she thought the only way to save humanity is to destroy it? If she despaired of defeating the Voidspawn, she might want to send everyone to the afterlife to prevent them from falling into their hands. And maybe our heroes could stop her by demonstrating that it is possible to defeat the coming Void incursion.

I dunno. I got some thinking to do.