[Spoilers for the Game of Thrones season 7 finale ahead!]
The minds behind HBO's Game of Thrones have known how the Wall would come down for years. During last night's dramatic season 7 finale, the Night King used an undead dragon to bring the wall crashing to the ground. After he killed Viserion in the episode 'Beyond the Wall', the Night King resurrected the giant creature and rode it, unleashing a blue flame that completely destroys a section of the wall. That allowed the White Walkers to push further into Westeros, in their ongoing efforts to overwhelm the living. The portion of the wall destroyed was Eastwatch-by-the Sea and left the fate of two characters up in the air.
With Game of Thrones season 7 being criticized for its timeline of events and general pacing, the showrunners (arguably) needed to do something dramatic to shock audiences in preparation for season 8. The season 7 finale brings multiple plot points and characters together, intertwining them ahead of the White Walker threat. The final six episodes of the show will see Westeros attempt to fend off the invasion of the undead - though main characters like Jon Snow will have other problems to deal with, too.
There were many revelations and reveals in the season finale, but the Wall coming down by an undead dragon was definitely the most dramatic. According to the show runners, however, they've known for years how to destroy the Wall for the White Walkers and Wights to come through. In a video delving into D.B. Weiss and David Benioff's thoughts about season 7 (see above), the pair revealed they've had this in the works for awhile:
"We tried to contrast to contrast the various season endings so they don't feel too similar. So last season we had a pretty triumphant ending with Dany finally sailing west towards Westeros... This one is definitely more horrific. For many years now we've known this would be the ending of the penultimate season. The Wall's kept these things out for 8000 years. There's no real reason why it can't keep doing that unless something puts a hole in the wall. There's one thing on the board from the beginning that is now big enough to do that, and that's a dragon. They just start to suggest itself as a logical way forward."
The pair have clearly been planning the reveal the destruction ever since the dragons were introduced to Game of Thrones. Both the show and its source material have explained that the Wall was imbued with magic to strengthen the giant structure, while also keeping out any threats coming towards it. So what does that tell us about the power of an undead dragon? The showrunners also mentioned that while it was easy to write the moment in their script, it was a little more difficult to bring it to life onscreen:
"We write 'and then the wall comes tumbling down' and it's really easy to type those words. It's really hard for them to make it look good. It needed to be a thing you go out of the season on."
If the pair had planned this reveal for years, it makes us wonder what else they've been working on. They're obviously skilled in long-form story telling, so it wouldn't be surprising if the next season brings back things from earlier on in the series. Game of Thrones won't return until sometime in 2018 (at the earliest) and the eighth season will only feature six episodes. But compensate this, some of the episodes will be feature length. Hopefully, the writers won't rush through the completion of the storylines for each character.
Game of Thrones season 8 premieres in either 2018 or 2019.