WARNING: SPOILERS AHEAD.
Since her debut in Season 2 of Game of Thrones, Brienne of Tarth has been considered a side character at best. But over the course of the series, she won viewers' hearts and became an unambiguous fan favorite. Brienne’s role as a figure of female empowerment—and one of the best swordfighters in all of Westeros—have been widely acknowledged, but less-discussed is the central role she’s played in the series’ plot.
Brienne has been around for some of the most pivotal moments in recent Westerosi history, including the Dragonpit summit and the Battle of Winterfell, but her impact on the overall plot of A Song of Ice and Fire run much deeper than that. Brienne hasn’t just interacted with most of the characters left standing for the final season of Game of Thrones—she’s directly responsible for many of them still being alive.
With the possible exception of Podrick Payne, no character in Game of Thrones has had their arc more directly affected by Brienne than Jaime Lannister. First and foremost, Jaime wouldn’t be around without Brienne to suggest that Catelyn Stark free him from captivity before the Karstarks could enact vigilante justice upon him—or to ferry him back to King’s Landing and protect him from peril.
Beyond his continued existence, however, Jaime also owes his redemptive arc almost entirely to Brienne. His time spent on the road with her changes him—and his decision to put himself in harm’s way to rescue her from the bear pit is the first truly good act he commits in the series. Their infamous shared bath scene marks the first time that Jaime ever got to talk to someone about his kingslaying incident, and thus she’s the first to recognize him for the hero he is. From there on out, Jaime does his best to live up to Brienne’s example—and she’s a large part of the reason why he comes to Winterfell to fight in the Battle for the Dawn.
Brienne of Tarth doesn’t formally meet Arya Stark until Season 7 of Game of Thrones—but she has a major impact on her storyline long before then. Brienne spends much of her own character arc searching for Arya after pledging to protect her, and when she finds her in the company of the Hound, she battles him to the death for Arya’s freedom.
Arya isn’t keen on travelling with Brienne at the time, so she bails from the scene before the fight concludes—but Brienne’s defeat of Sandor Clegane still frees her up to begin journeying on her own. Shortly after leaving the Hound behind, Arya catches a boat to Essos and begins her training as a faceless assassin—training without which she never would have been able to slay the Night King. Speaking of which, Arya ends up killing the Night King with a clever dagger maneuver that she’d practiced before—in a sparring match with Brienne.
Podrick Payne doesn’t just owe his current role in the Game of Thrones plot to Brienne—there’s a real good chance he wouldn’t even be alive without her. Following the exile of his previous lord, Tyrion Lannister, Podrick joins Brienne as her impromptu squire—and she begins to begrudgingly tutor him in the ways of the sword.
Pod has been attached to Brienne’s hip ever since. He’s accompanied her on her search for the Starks, to the siege of Riverrun, and eventually to the Battle of Winterfell. Along the way, he’s found himself in a number of armed confrontations—and it’s unlikely that he would have survived any of those encounters without Brienne’s patient instruction. More than that, Brienne took an aimless youth lost in the world and gave him a purpose in life.
Brienne of Tarth swears an oath to Catelyn Stark to find her daughters and protect them from harm—and Brienne continues to uphold that oath long after Catelyn’s gruesome death. After Sansa and Theon Greyjoy escape the captivity of Ramsay Bolton in Winterfell, it is Brienne who saves them from pursuing soldiers—and thus prevents them from returning to a fate worse than death.
After the rescue, Brienne takes Sansa to Castle Black so that she can reunite with Jon Snow—and that puts Sansa on the path to eventually becoming the Lady of Winterfell. Once there, it is the protective presence of Brienne that prevents Petyr Baelish from scheming so openly—and thus allows Sansa to eventually escape his manipulative influence.