Dragonglass is going to save the day. We've seen it kill White Walkers, which by itself is unspeakably awesome. We've known for some time that the people of the Seven Kingdoms will have to arm themselves with dragonglass weapons to stop the Night King and his army. In episode one of Season 7 of Game of Thrones, Jon Snow, the new King of the North, decrees that dragonglass must be mined for this very purpose. As it just so happens, Samwell Tarly has a revelation at the same time on the other side of the continent: They can mine Dragonstone for dragonglass.
Anyway, Sam is at the Citadel in Oldtown, from whence (because 'whence' feels appropriate in a Game of Thrones discussion) the maesters study the world. And he's just discovered a big book of everything we need to know about the series going forward, including the use of dragonglass as a cure for greyscale. Convenitently, Jorah Mormont is hangning out in the Citadel, seeking such a cure.
Odds on Sam Tarly curing Jorah Mormont? Seemingly amazing. According to the snippet of text we can see in the episode, dragonglass does it all. So, what are the implications of Sam's book, and what does it mean for the rest of this season (and, indeed, the series)? Let's find out.
Obviously, this list is dark and full of SPOLIERS.
We already know that dragonglass is super powerful. It kills White Walkers, and it was used by the Children of the Forest to create the White Walkers in the first place. They also utilize dragonglass to stop Benjen Stark from turning into a wight.
Well, in the premiere of Season 7, Samwell Tarly is having a tough time getting any of the maesters to listen to him about the coming of the Night King, so he takes matters into his own hands. He breaks into the Restricted Section of the library and steals a very old book.
It contains pretty much everything he (and by extension we) need to know about dragonglass. In fact, Redditor DapperBlueEyes broke down some of the relevant text from the book, including some oblique references to amulets and a Sacred Stone.
Among other things, we're told that dragonglass has potentially healing properties, from the text, "rendered dragonglass as a cure for," and "his great work on illness and dise–," as well as the phrases, "little harm incurs from the ingestion," and "on practical treatments." Taken together, it's pretty reasonable to assume we're going to see Jorah eat some dragonglass to cure his greyscale.
As Sam is tending to his disgusting duties, we get the pleasure of a telegraphed, yet no-less-annoying, jump scare, wherein a rotting arm thrusts out of a quarantined room towards Sam as he approaches, followed by a familiar voice. "Has she come yet? The Dragon Queen."
It seems Jorah Mormont has gone to the Citadel, in hopes the maesters know of a cure for greyscale. Or, in the less likely case that a maester-in-training will steal a book from the library that happens to contain a reference to his supposedly incurable terminal illness.
The book clearly reads, "...little harm incurs from the ingestion [of rendered dragonglass]..." and previously alludes to this being an Eastern practice, which the author discounts as "arcane" (read: nonsense).
But the author is wrong. And we have proof.
The show, and the books, paint greyscale as an incurable disease that slowly petrifies the afflicted to death. But we've known for some time of a greyscale (but sadly not fire) survivor, Stannis' daughter Princess Shireen.
Given her father's entanglement with Melisandre and the Lord of Light, you may have reasonably assumed the Red Woman used her fire magic to cure Shireen. But the show actually makes it clear Shireen was cured as an infant, long before Melisandre showed up. So, what if the fact that Shireen grew up on Dragonstone – basicaly a mountain of dragonglass – has to do with her beating the ailment?
Since it's unlikely the Baratheons actually knew of dragonglass's healing properties, we have to assume that trace amounts of the mineral are in the drinking water Shireen grew up ingesting, which kept the disease at bay. Keeping something at bay, however, is not the same as curing it.
In A Dance with Dragons, Val of the Free Folk (or Wildlings, if you want to be a jerk like that) tells Jon Snow, "The maesters may believe what they wish. Ask a woods witch if you would know the truth. The grey death sleeps, only to wake again. The child is not clean!"
It was the constant presence of dragonglass that stopped the disease in Shireen. Had she not been sacrificed, the greyscale likely would have resumed its deadly work, since she was displaced from Dragonstone.
So, is dragonglass really a cure-all magical substance? After all, it created the White Walkers. What other dangerous effects does it have? Does prolonged exposure to dragonglass cause people to go crazy, by chance?
The Targaryens initally ruled from their seat on Dragonstone, and when they were in power they split their time between their ancestral home and King's Landing. Daenerys's father was the Mad King, Aerys Targaryen, aptly named because he was dragonsh*t crazy. Is it possible that Aerys Targaryen went mad because of his lifelong proximity to dragonglass? Further, is it possible that his son Viserys (Daenerys's brother and tormentor in Season 1) experienced the same malady? If that's true, it's possible Dany avoided it because she left Dragonstone at such a young age.
And the Targaryens aren't the only ones who have occupied Dragonstone. Stannis Baratheon did, and he had his daughter burned at the stake so he could win a war and take over the world. That's more than a little crazy, isn't it? The Mother of Dragons better not make Dragonstone her permanent seat, or she just might fall to the same fate.