The grief might not be the member of the Nine, but the collective Taken themselves. We killed both Oryx and the Witness and left them with no leader. That's how engrained the need for a strong will to lead them is - they grieved without a King to lead them, until their collective prayers led to a new leader laying claim to the mantle. It would be terrifying if it turned out the Nine who blinded the Last City to Ghaul's assault, and the entity who now controls the Taken, are the same being. What limited the Nine was being made of dark matter, and they could still do things like culling the remaining, hidden Ahamkara after Riven was Taken, and blinding all the Last City's sensors to Ghaul's fleet. We are already seeing the effect of that influence gaining a foothold in reality if it is one of the Nine we're dealing with. If they gain enough power to fully step through the door...