I honestly doubt those were the four words.
It would be just like the giant to lead us on with a misleading comic title, the prophecy doesn't match up. Who is the right person? The V is not talking to the fiends, only out loud to herself. And how ultimate is arcane power with a finite time frame?
No I think they are on there way though
SpoilerV agrees to a plan put forth by the 'voices' that allows the soul bind to become permanent, (an epic spell Permanency comes to mind) explaining the choice to her mate, she utters the four words agreeing to the voices but directed at the mate. Her mate being the right person to confide such a choice with