User blog comment:Nomad27/Predictions of what will Occur in Volume 10./@comment-26815449-20160329235334/@comment-27359021-20160330001502

I think the whole Beast Kingdom business is because of Ainz. Slane Theocracy sent the Sunlight Scripture to Draconic kingdom to keep beastmen out. Ainz wipes out Sunlight Scripture, no Scripture to send to Draconic kingdom to fend off beastmen. Thus more hungry beastmen invading.

Of course, there might be another reason behind them, but I think if Demiurge had anything to do with this, the author would have dropped a hint somewhere.