

In Season 4, Jaime Lannister makes the quick expositional comment that "no one's made a new Valyrian steel sword since the Doom of Valyria," a very long time ago. In the books, there are a few more, and several family swords have been missing for ages. The known Valyrian steel blades on the HBO series include: Jon Snow's Longclaw, Brienne's Oathkeeper, Jaime's Widow's Wail (which really needs another name), Sam's Heartsbane, and Arya's unnamed catspaw dagger. Sam used a dragonglass dagger to kill a White Walker, but it actually might create them as well, which means that the living are going to need steel as well. Quick recap: fire and dragonglass kill wights, the blue-eyed zombies, and Valyrian steel kills the White Walkers who lead this undead army. Forging these swords is a lost art, but someone is going to have to make Valyrian steel on Game of Thrones if they want to defeat the Night King.

Unfortunately, the other type of weapon needed to defeat this enemy is much more difficult to replicate. In order to defeat the White Walkers on Game of Thrones, our heroes are going to need more than just dragonglass.
