Now that the face of evil incarnate in Westeros has obtained what we can all assume is an ice zombie dragon , the living, breathing people of the Seven Kingdoms are going to need something to be believe in. And the biggest glimmer of hope out there would be a way to kill the Night King once and for all. As Beric Dondarrion (Richard Dormer) reasoned in the middle of "Beyond," if someone can kill the army of the dead’s leader, they can eliminate the entire threat. Now, how did he realize that? By observing that killing one White Walker also killed every other wight he sired. Since the Night King created his entire army, logic would lead us to believe his death with result in every White Walker and wight's death.