As population increases, animal souls are promoted to human before they are spiritually advanced enough in terms of impulse control, etc.: this shouldn't have happened, but karmic progression is automatic, after all--it's a force of nature. But the 'animalization' of humankind bodes ill for civilization.
No doubt the same goes for elves, dwarves, and so on.
A dark necromancer has discovered a way of making the magical energy cost of resurrection less than the energy he can gain by draining their life force. Given a sufficient supply of mind-drained minions, ultimate power beckons.