Professor Slughorn From 'Harry Potter' Will Play A Major Role In 'GOT'

Season 7 of Game of Thrones may be arriving later than usual in the year, and only have seven episodes instead of 10, but they're still adding new locations to the map we've never seen before. This year, we'll be visiting Oldtown and the Citadel, where Sam is going to study to become a maester. With new settings come new characters, including a so-far-nameless archmaester, played by Jim Broadbent.

Broadbent ought to be familiar to fantasy fans, as he played a major role in Harry Potter and the Half-Blood Prince as Professor Slughorn. But who is this archmaester? And how will he affect the story to come?

Don't worry, he's not here to sort Sam into Slytherin. (Heaven forfend! Sam belongs in Hufflepuff, obvs.) But the lack of a name for the character suggests Broadbent will probably be an amalgamation of several of the archmaesters Sam and book readers meet at the Citadel, the most important of which is Archmaester Marwyn.

Marwyn the Mage is a name that pops up in the novels several times before we finally meet him. Mirri Maz Duur, the witch who Dany burns at the end of Season 1 for turning her husband into a zombie, mentions she was trained by Marwyn as part of her credentials. Former Maester Qyburn also speaks of Marwyn in a positive manner. From these testimonials, one might assume that Marwyn is a somewhat evil person.

But when Sam finally meets him in A Feast for Crows, Marwyn turns out to be a most open-minded man. Sam tells him all about the White Walkers beyond the Wall and how they can be killed with dragonglass daggers. Unlike everyone else in the South, Marwyn does not laugh Sam out of the room or call him deranged. Instead, Marwyn decides that with this news, he must go to meet Daenerys Targaryen (who is still in Essos) to warn her of the true enemy, and leaves the Citadel at once for Meereen.

Now, with Daenerys already in Westeros, obviously that last part isn't going to happen. Also, since Broadbent says he filmed five major scenes, all of which are with Sam, we assume he's not dropping everything and running to Dragonstone either.

So why does this matter? Well, there's this fan theory. (Isn't there always?)

It's called "The Grand Maester Conspiracy." It says the maesters have been working to undermine dragon-based magic, and the Targaryens, ever since they conquered three centuries ago. The books have been hinting around that it's true, including a scene in A Dance With Dragons where Lady Dustin says in front of Reek that the Maesters were responsible for convincing Rickard Stark to set up the intermarriages between Houses Stark, Baratheon, Arryn, and Tully as a way to unite those houses to overthrow the Targaryens, that ultimately lead to Robert's Rebellion.

Unlike some of the other archmaesters we meet in the books, who deny all this, Marwyn believes this conspiracy to be true. He even tells Sam the maesters are responsible for the deaths of the dragons, which jives with other suggestions in the novels that it was they who convinced the Targaryens to chain up their dragons until they became as small as dogs and then stopped breeding altogether.

The maesters have also supposedly been hoarding magical implements at the Citadel, in order to increase their power. (One which we see is in Marwyn's office, it's an obsidian candle that burns cold.) These could be extremely useful for Sam, especially if he heads back to rejoin the fight against the Night King by the end of the season.

There's one more point, though, I expect the show will drop. Marwyn has a couple of novices who hang around him, and are involved in the scene where Sam tells all about the Night King. One is Alleras, who is believed to be an extraneous Sand Snake, disguising herself as a boy in order to gain an education. The other, a young man named Pate, was killed prior to Sam meeting him and has been replaced by a Faceless Man. Said Faceless Man is actually Arya's pal Jaqen H'ghar, and is floating about in the background, obviously biding his time before a kill.

With only 13 episodes to go before the end of the series, we doubt the show will bother with either of these subplots. But it's good to have them floating about in the back of your mind, just in case Broadbent is killed out of the blue in his final scene.

Game of Thrones Season 7 returns this Sunday, July 16, at 9 p.m. ET, on HBO.