If something was to happen to The Mother, would that be the end of all demons? I am not sure that The Mother can be killed, but if she was.
Well, all the demons that currently exist would remain. And then, once they found out what happened...
Chaos. Carnage. All restrictions on rage, hunger, death would be removed. They would sweep across the world, and if anything remained afterwards the remaining demons would be so powerful from their feast that they could stomp it out effortlessly.
A united demonic front. And then no more demons are ever created.
What a price to pay, for such a goal...
-Musings of the Demon Master Dzu