The neutral creatures don't increase in numbers anymore; they all (or almost all) have a growth limit. They'll stay as they are, so you can safely build up your army and kill them, as there's plenty of everything for that.
But the worst thing is that the quests for the sulfur and mercury mines can't be completed: apparently, it's a coincidence: I didn't have 10 mercury at once + I already met the human spy. So – everything from the beginning:mad: