Game of Thrones season 8 may see Sam Tarly and Gendry discover the means of forging new Valyrian steel, crafting from it weapons to use in battle against the Night King and his army of the dead. There hasn't been any Valyrian steel created in centuries, not since The Doom destroyed that ancient civilization, but Sam does have a book detailing weapons that can harm the undead.

With the final season of Game of Thrones fast approaching, it's anyone's guess just how the epic series will conclude. There are certainly some things which are expected to happen in Game of Thrones season 8, like the Battle of Winterfell and a fight to wrest control of the Iron Throne from Cersei. Beyond those broad strokes, however, most details about the HBO series' final season are being kept tightly under wraps. This secrecy has led to dozens upon dozens of theories, including this one about Sam and Gendry being the key to forging the first Valyrian steel swords in centuries.

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A new crop of Valyrian steel swords could give a real advantage to those fighting against an enemy as seemingly invincible as the White Walkers. And while Sam and Gendry may not appear to be crucial players in this final battle, they may actually be two of the most important characters if they can figure out how to forge new Valyrian steel. Here's how it could happen.

Valyrian Steel Explained

Valyrian Steel Jon Snow and Brienne of Tarth

Valyrian steel is unlike any other material in the world of Game of Thrones. It's an extremely durable material and is resistant to fire (with a possible exception for dragonfire). Blades forged with Valyrian steel are sharper and lighter than any castle-forged steel, never losing their edge. Valyrian steel blades also have a distinct ripple pattern to them that comes from the thousands of times the steel is folded back on itself during its forging.

In addition to dragonglass, Valyrian steel (also referred to by some as dragonsteel) is the only other material known to be capable of killing White Walkers. Similarly to when Sam slays a White Walker with a dragonglass dagger in Game of Thrones season 2, Jon also kills a White Walker with his Valyrian steel sword, Longclaw in the season 5 episode, "Hardhome".

Valyrian Steel Hasn't Been Forged In Centuries

Two Swords Valyrian Steel Game of Thrones

Along with being so renowned, Valyrian steel is also incredibly rare and expensive. As its name implies, the steel was originally forged in Valyria, the ancient civilization from which the Targaryens are descended and who first bred dragons, using them along with other magics to conquer much of Essos. The Valyrian Freehold spanned from Pentos in the east to Old Ghis in the west and lasted for centuries until The Doom - a devastating event that shattered the peninsula, sending Valyria and its neighboring cities into the ocean. The cause of The Doom is unknown, but many believe it was a result of all 14 of Valyria's volcanoes erupting at once.

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When Valyria fell and was consumed by the Smoking Sea, all their vast knowledge was lost - including the means of forging Valyrian steel. Legends say that magic spells and possibly even dragonfire were a part of this intricate process, but no one has successfully forged Valyrian steel since The Doom. There are a few skilled blacksmiths who can manage to re-forge blades from already existing Valyrian steel - as seen in the Game of Thrones season 4 episode, "Two Swords" when Tywin Lannister has the ancestral Stark sword, Ice, melted down and re-forged into Oathkeeper and Widow's Wail - but even that remains an arduous and complicated process.

Page 2 of 2: HOW SAM & GENDRY WILL FORGE NEW VALYRIAN STEEL

Only A Handful Of Valyrian Steel Swords Exist

Before The Doom of Valyria, the noble houses of Westeros would purchase Valyrian steel swords and a few still survive today as family heirlooms. Perhaps the most famous on Game of Thrones is Ice, the greatsword of House Stark and the blade Ned Stark would wield when dealing the king's justice (as seen in the season 1 premiere). Sadly, Ice is probably best known for also being the weapon later used to behead Ned by Ser Ilyn Payne. Ice was then melted down and re-forged in to two longswords - the aforementioned Oathkeeper and Widow's Wail. Currently, Oathkeeper is with Brienne of Tarth while Widow's Wail went to Jaime Lannister following Joffrey's death.

Jon Snow also famously wields a Valyrian steel sword, Longclaw, which he was given by Lord Commander Jeor Mormont in Game of Thrones season 1 as thanks for saving his life from a pair of wights. Longclaw is the ancestral blade of House Mormont, but since Mormont's son, Jorah, had dishonored the family, Jeor felt it appropriate to pass the sword on to his steward, Jon. To better suit its new owner, Mormont had Longclaw's pommel refashioned from a bear (the animal on House Mormont's sigil) into a white wolf reminiscent of Jon's direwolf, Ghost (not to mention, the animal on House Stark's sigil).

Related: Game Of Thrones: A Breakdown Of House Alliances And Feuds

The only other known Valyrian steel sword belonging to a noble house of Westeros is Heartsbane - the sword of House Tarly which Sam stole when he last visited his family at Horn Hill in season 6. In addition to the swords, there is also a Valyrian steel dagger (sometimes referred to as the Catspaw dagger) which was used in the assassination attempt on Bran Stark in Game of Thrones season 1 and was later revealed as having belonged to Littlefinger. The Valyrian steel dagger is now in Arya Stark's possession, with her using it to execute Littlefinger in season 7.

Theory: Sam & Gendry Will Forge New Valyrian Steel

Sam sitting behind a desk in the Citadel in Game of Thrones

Just four Valyrian steel swords and one dagger aren't going to be enough to fight the Night King and his fellow White Walkers, let alone kill them. The living may have a couple of dragons and tons of dragonglass, but forging new Valyrian steel swords could be the real difference maker in the war. In which case, it's great news that not only are these five remaining Valyrian steel weapons already at Winterfell (where the impending battle with the Night King's army is expected to take place), but the two people best suited to figure out how to forge new Valyrian steel are also there - Sam and Gendry.

It's true that when Valyria fell, the means for making Valyrian steel was lost. However, in Game of Thrones season 7, Sam steals a book from the Citadel's restricted section that details the trove of dragonglass Jon and Daenerys later find in the caverns on Dragonstone. That same book also includes an illustration of the Catspaw dagger and mentions how the Targaryens would use dragonglass to decorate the hilts and pommels of their weapons. And while none of this serves as definitive proof that this same book also includes information on Valyrian steel, if that information exists anywhere, it'll be in that book. Though, reading about how to forge Valyrian steel and actually doing it are two very different things.

Game of Throne Gendry Blacksmith

This is where Gendry comes in. When introduced in Game of Thrones season 1, Gendry is working as an apprentice to a famed blacksmith in King's Landing, Tobho Mott. Originally from Qohor - a free city in Essos known as the City of Sorcerers which was part of the Valyrian Freehold - Mott is one of the few smiths who knows how to rework Valyrian steel. In the novels, it's Mott who Tywin tasks with re-forging Ice, though on Game of Thrones it's some unnamed smith, presumably because the actor who plays Mott was unavailable. Regardless, if Mott knew how to rework Valyrian steel, having learned the technique in his native Qohor, then it stands to reason that Gendry might also be at least somewhat familiar with this technique.

When Sam left Oldtown, he brought many of the books he stole from the Citadel with him - the one which mentions Rhaegar anulling his marriage to Elia Martel, but also the book which might hold the secrets of Valyrian steel. In the Game of Thrones season 8 trailer, Gendry is seen hard at work in Winterfell's forge, and while it's impossible to know for sure, it's plausible that he's hard at work forging new Valyrian steel. Plus, Daenerys' dragons are at Winterfell, so if dragonfire really is a requirement in forging this mythical steel, they've got it. If there was ever a time for new Valyrian steel to be forged on Game of Thrones, this is it - and with the great war now upon them, it's not a moment too soon.

More: What to Expect from Game of Thrones Season 8

Game of Thrones season 8 premieres Sunday, April 14 on HBO.