WARNING: Major Spoilers ahead for the latest episode of Game of Thrones! Continue reading at your own risk...
Last night's episode of Game of Thrones taught viewers - and characters - a lot about the evil that lives north of the wall.
The Night King is powerful enough to take a knock a dragon out of the sky with just a spear and, on top of that, he can also use his power to bring the creature back to life to make it part of his army.
It was also revealed that killing a White Walker will result in killing any wight that has been turned by that specific White Walker. With that in mind, Jon Snow and the others will be scrambling to figure out every possible way these powerful beings can be brought down.
Fortunately, they already have more than one option.
Much of Jon's mission this season has revolved around getting dragonglass to stop the White Walkers, so it's been made very clear that it's one of the ways to kill them.
The reason that this substance can take the life of a White Walker is that it's actually the very thing that gave them life in the first place.
When the Children of the Forest created the White Walkers a long time ago, they inserted a piece of dragonglass into the heart of a man. This kept him moving and thinking like a living being, but gave him an array of undead powers and abilities.
Luckily for Jon Snow, an enormous deposit of dragonglass sits beneath Dany's castle, and she's allowed him to mine as much as he needs.
Valyrian steel, like dragonglass, is an extremely rare commodity in Westeros. Unfortunately, it isn't likely that there is a hidden mine of this metal hiding out somewhere.
As of now, there is a very finite amount of Valyrian steel in existence, since Valyria is no more. With great skill, new weapons can be forged by melting down other Valyrian steel swords, but nothing can be made from scratch.
What does help is that there are a few Valyrian weapons currently floating around Westeros.
Ned Stark had a Valyrian steel sword named Ice. After it was used to behead him, Tywin Lannister had two separate swords forged from its metal. Oathkeeper was given to Jaime, who later gave it to Brienne of Tarth. Widow's Wail was made for Joffrey, but was passed onto Jaime after his death.
Jon Snow has a Valyrian steel sword named Longclaw, which was given to him by Jeor Mormont. Jon tried to give it to Jorah Mormont in the last episode, but Jorah insisted that the King in the North keep it.
Samwell Tarly stole the Valyrian sword named Heartsbane when he left his father's house en route to Oldtown.
There is also a Valyrian steel dagger floating around Winterfell at the moment. The weapon was used to kill Bran back in the first season, so Littlefinger gave to the only remaining Stark man as a gift. Bran had no use for it, so he gave it Arya. In the latest episode, Arya handed it over to Sansa.
The wights are much easier to kill than White Walkers, and any weapon could do the trick. However, as we learned in this past episode, fire is incredibly effective.
Unlike the White Walkers, wights aren't exactly of a sound mind. They seem to be more intelligent than the typical zombie, but the blood-thirsty concept is still the same.
The biggest problem with the wights is their sheer number. The Night King has turned thousands upon thousands of people - and apparently giants and animals - into these things, and they'll do his every bidding.
By killing a White Walker however, many of the wights can be taken out with one swing of the sword. That's just much easier said than done.