Catelyn Stark has been dead for three seasons on Game of Thrones, but as Sunday night's episode proved, she's hardly been forgotten.
The former Lady of Winterfell was all Jaime Lannister and Edmure Tully could talk about in "No One," as Jaime recalled how Catelyn, like his sister/lover Cersei, would do anything for her children. Game of Thrones is rarely subtle or sentimental, so it appeared that the long-awaited introduction of Lady Stoneheart was finally imminent. But those dreams were dashed later in the episode when the Hound came across the man, the myth, the legend among legends himself, Beric Dondarrion, leader of the Brotherhood Without Banners, in the Riverlands.
To further explain why this is significant, you have to agree to the spoiler terms and conditions, as laid out by our bear:
If Lord Beric Dondarrion is alive, then there's no Lady Stoneheart. Plain and simple. In the books, Beric sacrifices his life to resurrect Catelyn three days after the Red Wedding. She quickly lays waste to Lannister allies in the Riverlands as the mute outlaw Lady Stoneheart. It's a major plot point in the books, as Stoneheart crosses paths with Brienne, Pod, and a couple of Freys during her various murder sprees.
However, the show is clearly headed down another path. Edmure mentioned that he had been held prisoner by the Freys for years, so if Lady Stoneheart hasn't been resurrected by now, it seems unlikely that Beric would be able to do the deed years after her death given the state of her decomposed body. Then, there's also the fact that according to Beric's serene, riverside chat with the Hound, the Brotherhood is heading up North to battle the White Walkers. This, of course, is very different than George R.R. Martin's current plans for the Brotherhood.
It's more likely that showrunners David Benioff and D.B. Weiss are using other means to get to the same conclusion. As Vanity Fair pointed out, we saw some of Catelyn's story play out with the Blackfish. In the books, Lady Stoneheart takes Brienne for a Lannister spy because of her Lannister armor and sword. She even orders her to be hanged. However, in this episode, it was the Blackfish took Brienne for a potential spy when she tried to hand him Sansa's letter. (To be fair, he said he hadn't seen Sansa since she was just a girl, so it's not like we blame the guy for being a bit suspicious in the middle of a siege.)
There's also something to be said for the way Beric and his right hand man, Thoros of Myr, hang the three rogue members of the Brotherhood Without Banners who went off and killed Brother Ray and his happy hippie commune. This is some expert trolling from Benioff and Weiss, as we know how fond Lady Stoneheart is of hanging her enemies.
Lady Stoneheart symbolizes an all-consuming need for vengeance, and while it would be incredibly satisfying to watch the Freys get their comeuppance at the hands of Catelyn Stark, it wouldn't make sense to introduce such a divisive character so late in the game. At this point, the plot needs to move forward, not meander through the Riverlands.
Frankly, the Brotherhood is needed in the North, where the Hound can finally use his talents for the greater good of humanity. Plus, if Arya's time in Braavos and the Great Cleganebowl Rally of 2016 proved anything, it's that your crazy-complex fan theories hold no weight in Benioff and Weiss's world.