Be aware this post has MAJOR SPOILERS for Game of Thrones through Season 7, Episode 7, "The Dragon and The Wolf".

"Don't knock it down while I'm gone." - Jon Snow, "The Door"

The Checkov's gun of Game of Thrones finally went off. You don't introduce a big ass magical wall protecting the realm of men from the icy undead unless you intend to bring it tumbling down, and that's just what the series did this week when the Night King rode Viserion, his newly minted wight dragon, to the wall and melted a path right through it. Fans have long speculated whether dragon fire or wildfire would be enough to burn through the wall, and it turns out the blue flames of an ice dragon was just the ticket to finally get the job done. It was a necessary narrative pay off and we all knew it had to happen, but what does this mean for Jon, Daenerys, and the fate of humankind? Nothing good, especially considering the queen of Westeros is willing to watch her kingdom freeze over as long as she keeps the throne.

With the Night King's forces about to unleash havoc on the realm, let's look back in memorium at the wall that protected Westeros for centuries, how it came to be, and all the other little details you may have forgotten along the way.

The History

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Image via HBO

The Wall is a 700-foot all, 300-foot thick structure that spans 300 miles along Westeros' northern border, from the Bay of Seals in the east to the Gorge in the west. Legend has it the was built from ice, stone, and earth (and some magic, but we'll get into that), 8000 years before the events of A Song of Ice and Fire, erected by King Brandon Stark, a.k.a. Bran the Builder, to protect the Seven Kingdoms against White Walkers and other creatures of the Great Other. 

"Almost seven hundred feet high it stood, three times the height of the tallest tower in the stronghold it sheltered. His uncle said the top was wide enough for a dozen armored knights to ride abreast," we learn from Jon Snow's perspective in A Game of Thrones. "The gaunt outlines of huge catapults and monstrous wooden cranes stood sentry up there, like the skeletons of great birds, and among them walked men in black as small as ants."

A legendary member of the First Men, Bran the Builder also constructed Winterfell and founded House Stark, and there are lots of folks who are convinced that the ancient Bran and our weird little Three-Eyed Raven are in fact the same Bran. The speculation suggests that the present day Bran will get timey-wimey again and travel back in time in an attempt to stop the White Walkers and discover that via closed-loop logic, he was the one who built the Wall all along. I've been a doubter of this theory, but HBO fanned the flames when they released a DVD extra about the history of Westeros, which includes a sketch that indicates Bran the Builder may be paralyzed as well.

The Magic

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Image via HBO

The Wall wasn't just built with mundane means. Legend has it Bran the Builder had a little help from Giants and the Children of the Forrest to build and fortify the safeguard of the realm. It's not just a physical deterrent, there are magic spells included in the Wall that prevent the Night King and his fellow undead army from crossing the threshold.

"The Wall is not just ice and stone," Benjen Stark, a.k.a. Coldhands, tells Bran and Meera in the Season 6 finale. "Ancient spells were carved into its foundation, strong magic to protect men from what lies beyond. And while it stands, the dead cannot pass."

This line led most people to believe (including yours truly) that Bran, freshly marked by the Night's King, would undo that magic when he crossed through, just as he did at the Three-Eyed Raven's cave in "The Door". However, it seems that melting down the Wall (and presumably some of those carved spells) was enough to render the magical protection null and void.

The Night's Watch

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Image via HBO

The Wall doesn't just protect the realm, the realm protects the Wall with the help of the Night's Watch. A sworn brotherhood and military order of men from all walks of life, The Night's watch defends the Wall from the dangerous forces in the Northern wastelands. Once a Brother of the Night's Watch takes the Black, he serves for life, sacrificing family and fortune to become a watcher on the wall. The punishment for abandoning the oath is death.

The oath reads:

"Night gathers, and now my watch begins. It shall not end until my death. I shall take no wife, hold no lands, father no children. I shall wear no crowns and win no glory. I shall live and die at my post. I am the sword in the darkness. I am the watcher on the walls. I am the fire that burns against the cold, the light that brings the dawn, the horn that wakes the sleepers, the shield that guards the realms of men. I pledge my life and honor to the Night's Watch, for this night and all the nights to come."

As such, the Night's Watch is made up a rather diverse bunch. There are volunteers from the noble houses who give up their claims to wealth with pride, bastards, outcasts, and common criminals who chose a life on the wall over a life in a dungeon. The amount of proud volunteers dwindled over the millennia, meaning the ranks of the Night's Watch are disproportionately filled by rapists, muderers and thieves. That also means they can be a dangerous and unwieldy bunch, as proven by not one, but two deadly insurrections against the Lord Commander of the Night's Watch. First against, Jeor Mormont and then Jon Snow.

"The Night's Watch has forgotten its true purpose, Tarly," Mormont tells Samwell Tarly in A Storm of Swords. "You don't build a wall seven hundred feet high to keep savages in skins from stealing women. The Wall was made to guard the realms of men...and not against other men, which is all the Wildlings are when you come right down to it. Too many years, Tarly, too many hundreds and thousands of years. We lost sight of the true enemy."

And if the Night's Watch has lost sight of its mission, it has also lost the numbers needed to effectively guard the giant fortification. The Wall is peppered with 19 fortresses and castles along its path and while the Watch used to draw enough recruits to fill most of them, there are now only enough men to guard three;  Castle Black, Eastwatch-by-the-Sea and the Shadow Tower. It's unclear what function the Night's Watch will serve now that the Wall is compromised.

The Inspiration

Image via HBO

This doesn't have anything to do with the show's mythology, but George R.R. Martin says the idea for the Wall came from a visit to the historical site of Hadrian's Wall in Carlisle, England.

In a 2014 interview with Rolling Stone, Martin explained,

"I can trace back the inspiration for that to 1981. I was in England visiting a friend, and as we approached the border of England and Scotland, we stopped to see Hadrian's Wall. I stood up there and I tried to imagine what it was like to be a Roman legionary, standing on this wall, looking at these distant hills. It was a very profound feeling. For the Romans at that time, this was the end of civilization; it was the end of the world. We know that there were Scots beyond the hills, but they didn't know that. It could have been any kind of monster. It was the sense of this barrier against dark forces – it planted something in me."

Hadrian's Wall is about 73 miles long with varying width and height up to about 10 feet wide and 20 feet tall.

The Extras

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Image via HBO

In the books, there is also something called the Horn of Joramun, a.k.a. the Horn of Winter. Not much is known about the horn, but Joramun was a legendary King Beyond the Wall who is said to have united the Free Folk and help Brandon Stark defeat the Night's King. It is said that when Joramun blew his horn, he woke giants from the Earth. According to Ygritte and Mance Rayder, if the horn were to be blown again, it would bring the wall down.

Mance Rayder is said to have found the Horn of Winter, but it is later revealed that his horn was a fraud. Ygritte, Mance, Dalla, Jon, and Tormund all talk about the horn in the books and in A Dance of Dragons, Mellisandre thinks to herself, “The Horn of Joramun? No. Call it the Horn of Darkness. If the Wall falls, night falls as well, the long night that never ends. It must not happen, will not happen!” So so there's some pretty major mythology built around this horn. In the books, Sam has also been carrying around a broken horn that Martin is keen to mention with notable regularity so that has sparked the interest of fan theorists for years. Sam does find a horn in the show (when he discovers the dragon glass at the Fist of the First Men), but it's never mentioned so it seems like a nod to the books.

There's also another horn floating around in the ASOIAF books that may have an important role to play. Euron Greyjoy discovers a horn called Dragonbinder; a six-foot instrument cased in Valyrian steel and inscribed in Valyrian Glyphs, which glow red and white when blown. However, that inscription reads "“I am Dragonbinder … No mortal man should sound me and live … Blood for fire, fire for blood,” which means anyone who blows the horn dies. Both of the horns have been built up as important, potentially game-changing pieces in the books, but they've never been mentioned in the show so at this point it's pretty likely they have no role in the series.