Dragonglass and Valyrian steel are hugely important in the Battle of Winterfell and in any conflict against the wights and White Walkers. Here’s a look at just what it takes to kill wights (who are raised from the dead) or White Walkers, who are created from Caster boys by the Night King on Game of Thrones.
Wights are much easier to kill than White Walkers, although they’re still very dangerous. You can stab them with Dragonglass, stab them with Valyrian steel, or set them on fire to kill them. Or, if you kill the White Walker who resurrected the wights, then all the wights under his command will automatically die. (Interesting note: dragonglass is useless against wights in the books, although it works in the show.)
White Walkers, on the other hand, are tougher to kill. Only dragonglass or Valyrian steel will do it. Sam first discovered dragonglass was the key by accident. Then at the Hardhome battle, we learned that Valyrian steel will destroy White Walkers too. Jon Snow, Jorah, Brienne, and Jaime all have Valyrian steel swords, and Arya has a Valyrian steel dagger that Bran gave her.
We don’t know yet what dragon fire will do. Bran admitted that dragon fire has never been tried on a White Walker, so its effect is still unknown.
The Night King is still unknown. He may have special magic the White Walkers don’t have, since he was directly created when the Children of the Forest plunged dragonglass into his heart thousands of years ago, when he was a First Man.
Here’s a quick refresher on how dragonglass works.
Dragonglass is a type of volcanic glass, also known as obsidian. Valyrians once called it “frozen fire.” Although folklore holds that dragonglass is made by dragons, Maesters believe it is just a type of volcanic rock. It was also used by the Children of the Forest to create the Night King. Sam found a cache of dragonglass at the Fist of the First Men in Season 2. In Season 5, dragonglass was found at Dragonstone by Stannis.