‘Game of Thrones’ 101: What Can Kill White Walkers, and What Exactly is Dragonglass?

Winter is here and with it come the undead White Walkers — so how will the Seven Kingdoms stop them?

(Note: This post contains spoilers for all of “Game of Thrones” through season 6.)

Season 7 of “Game of Thrones” will have plenty of battles, including more spats with the Night King and his White Walkers, a group of monster ice people that lead an army of the undead.

White Walkers are pretty close to unkillable, but a few characters on the show have bested them. With the right weapons, the White Walkers go down just like anybody else. Unfortunately, those weapons are pretty rare.

But there are two known substances that can kill White Walkers: Dragonglass and Valyrian steel. The latter is forged into a handful of swords that are scattered among the Great Houses of Westeros. The former is a tough-to-find rock that not a lot of people know about.

In a flashback in Season 6, we learn that the magical Children of the Forest first used Dragonglass to create the Night King thousands of years ago, when they were at war with the First Men. Due to some confluence of magical consequences, it seems that the stuff that created the White Walkers is also some of the only stuff that can destroy them.

So what exactly is Dragonglass? In the parlance of our world, it’s obsidian, a form of black volcanic glass. In Westeros, where the show takes place, it’s fairly rare. Samwell Tarly (John Bradley-West) first discovered a cache of Dragonglass weapons north of the Wall at the Fist of the First Men, and it was Sam that first managed to, somewhat accidentally, kill a White Walker with an obsidian dagger. Likewise, when the army of the dead assaulted the cave of the Three-Eyed Raven in season 6, Meera Reed jabbed a Walker with an Obsidian-tipped spear and was shocked when that turned him into a million tiny pieces of ice.

Dragonglass is hard to come by, but as it turns out, there’s one place in Westeros where the stuff is available in large quantities: Dragonstone. The small volcanic island and its castle were previously held by Stannis Baratheon (Stephen Dillane). We know from the trailers for “Game of Thrones” Season 7 that Daenerys will be landing at Dragonstone when she finally makes it across the Narrow Sea to Westeros.

So with Dragonstone in play, there’s at least a possibility that the Seven Kingdoms will be able to get hold of enough Dragonglass weapons to stand a chance against the White Walkers before the big battle.

For a while, it seemed to the Jon Snow (Kit Harrington), Sam and the rest of the Night’s Watch that Dragonglass was the only way to kill a White Walker, and weapons made of the stuff were in extremely short supply. But when the Night’s King attacked Hardhome, the wildling city north of the Wall, Jon discovered that his Valyrian steel sword Longclaw was also capable of killing a White Walker.

Valyrian steel is extremely rare, mostly because the means of forging it was lost to history. Legend has it that Valyrian steel was made using dragon fire and magic spells — but since Valyria was destroyed by the Doom hundreds of years ago, and there haven’t been any dragons up to now, the secrets of how to make more of the stuff went with the city.

We know of only a few Valyrian steel blades in the Seven Kingdoms. Jon’s Longclaw is one; Brienne of Tarth (Gwendoline Christie) has another called Oathkeeper; Sam stole the Tarly family Valyrian steel sword Heartsbane and took it with him to Oldtown. There’s also Widow’s Wail, the sword Tywin Lannister (Charles Dance) first gave to King Joffrey (Jack Gleeson) and which passed to King Tommen (Dean-Charles Chapman) when Joffrey died. We’re not sure where it is now that Tommen is also dead.

In the “A Song of Ice and Fire” books, there are other Valyrian steel swords, but we haven’t seen them factor into the show yet. It’s still possible they’ll show up, however.

It’s also worth noting that while Dragonglass is effective against White Walkers, shattering them into ice, they’re useless against the undead army of wights the Walkers are bringing with them. Regular steel swords can handle the dead, as can fire, but the relatively weaker obsidian is actually a liability against them.