The following contains spoilers for Game of Thrones season seven.
It's no secret that the White Walkers have proven to be the most dangerous threat on Game of Thrones. Their ability to create an army of undead makes them virtually unstoppable, but we find out in season seven's sixth episode, "Beyond the Wall," that they do have a weakness.
When a White Walker dies, all of the wights it created die too, meaning an entire army could be destroyed in just a few blows. But how many more White Walkers do they need to take out in order to defeat the Night King's army once and for all? The answer is three.
In the episode, we see Jon Snow take down one of the four White Walkers, but there are still the Night King and two other White Walkers that make it out of the battle alive. Although this seems like a small number, we can't forget that they still have a huge army of wights — which now includes a dragon — on their side. If there's anyone who can find a way to take them down, though, it's Jon Snow and Daenerys Targaryen.