The Door (Season 6, Episode 5)
Skipping straight over the fifth season, the next most important episode to rewatch is "The Door" - and it's a heartbreaker. It may seem excessive to jump a full season, but "The Door" is actually the perfect episode to serve as catch-up, covering all the most important characters and what they've been up to since "The Children." Sansa, now at the Wall, has been taken from King's Landing to the Vale, then married to Ramsay Bolton, then escaped to the Night's Watch - and all of this is covered in a conversation with Petyr Baelish. Jorah reveals that he is in love with Daenerys but has Greyscale (a plot point that should have been far more important than it ended up being), and Yara and Theon make an appearance, in the Iron Islands, attempting to claim the throne.
Meanwhile, Tyrion and Varys are ruling Meereen in Daenerys' stead, and Arya is training with the Faceless Men. In both cases, this episode sets up a lot of what can be expected in the final season; Arya's training sets her up as the killer that she becomes, and in Meereen, we're shown how Tyrion and Varys can become the reason and diplomacy behind Daenerys' throne.
Of course, there's one more vital scene in this episode, and it's the one that gives "The Door" its name. Bran completes his training with the Three-Eyed Raven, but accidentally gives the White Walkers access to the cave under the tree - bringing them in. While he is having visions, the dead attack, and Bran wargs into Hodor to have him hold the door and keep the dead away so he can escape. Heartbreaking, true - but also revealing. This is the moment that Bran stops being Bran and becomes the Three-Eyed Raven. This is the moment that the audience learns that Bran can impact other times, and that his visions can affect the real world. And this is the moment that everyone cried at the death of one of the purest characters on the show.
Battle Of The Bastards (Season 6, Episode 9)
From plot-heavy episode to one that is all about the battle, it's time for "The Battle of the Bastards". This episode does include one important scene in terms of plot, as Daenerys shows how she will deal with 'negotiations' (burn them all, essentially), and Yara and Theon arrive in Meereen to pledge their allegiance to her. However, this episode is all about the fight scene, as Jon Snow and Ramsay Bolton battle it out.
This episode isn't just included because it's a truly epic fight scene, though. It reveals a whole lot about what's happening with the Starks. Sansa has learned how to play the game and has summoned the Knights of the Vale, Jon Snow is still rushing off to do the right thing even though it will probably get him killed, and Sansa goes full-on Dark Sansa and feeds her abusive husband to his own hounds. In addition, this episode was directed by Miguel Sapochnik, who will be returning in the final season to direct the Battle of Winterfell, when the armies of the living and the dead finally come together.
Winds Of Winter (Season 6, Episode 10)
Two episodes in a row - but for very good reason. After "The Battle of the Bastards" covers what is going on in the North, it's time to take a look at what's happening in the South at the end of the sixth season. "Winds of Winter" is another fairly plot-heavy episode, but it also includes the biggest non-battle death scene in the series, and shows just what Cersei is truly capable of.
We're referring, of course, to the explosion of the Sept of Baelor, which Cersei orchestrates rather than stand trial there. This kills off the Tyrells, the Faith Militant, and indirectly, Tommen, who steps out of a window in a beautifully quiet death scene. This is hugely important for the final season, not just because it wipes out the Tyrell threat to the throne and the last of Cersei's children, but because it marks the moment that she truly becomes the darkest version of herself - nothing left to live for but to kill her enemies and sit on the throne.
In addition, there are a lot of other major plot points that come up in this episode. Sam arrives at the Citadel, Daenerys leaves Meereen for Westeros, Arya returns to Westeros and murders Walder Frey, Littlefinger reveals he wants the throne, Jon marshalls an army against the White Walkers, Bran gets back to the Wall, and Davos confronts Melisandre about burning a child at the stake.
This is also the episode that revealed the truth about a long-held fan theory; Jon Snow's true parentage, which makes him the trueborn son of Lyanna Stark and Rhaegar Targaryen, and the heir to the Iron Throne.
Dragon And The Wolf (Season 7, Episode 7)
Finally, no rewatch would be complete without the season 7 finale - to catch up on where everyone is now. 'The Dragon And The Wolf' covers an impressive amount (unsurprising for a Game of Thrones season finale), starting with the meeting at King's Landing, where all the major players for the Iron Throne come together for the first time. This episode covers the current state of alliances, pregnancies, and relationships. It sees the end of Littlefinger at the hand of the Starks at Winterfell, and Jon and Daenerys finally getting it on (which is a perfect way to follow up 'Winds of Winter', when it is revealed that they are actually related).
The most important moment, though? The Wall finally comes down, thanks to Ice Viserion, and the Battle for Westeros is about to begin.