Bran Stark is undeniably one of the most important characters in A Song of Ice and Fire. Excluding the prologue, his is the first point-of-view chapter in the entire series. He acts as George R.R. Martin's main vehicle to explore the magic of the world. And, per A Song of Ice and Fire's now concluded HBO adaptation, Game of Thrones, Bran will end up as King by the end of the series.
However, in Game of Thrones, Bran, played by Isaac Hempstead-Wright, tends to take on a much less important role than his book counterpart. Show Bran's storylines tend to fall to the wayside in favor of other characters, to the point where Bran misses an entire season. Unlike any other leading character who's survived up to that point, Bran is entirely absent from season 5.
While Bran's exclusion from season 5 makes him stick out like a sore thumb in comparison to the rest of the cast, it parallels some of Martin's books, specifically the fourth and fifth novels in the series, A Feast for Crows and A Dance With Dragons.

Bran before season 5
Bran kicks off the series as an adventurous young boy, climbing the walls of Winterfell. However, his climbing days end prematurely, when he accidentally stumbles upon a secret, catching Cersei Lannister (Lena Headey) having sex with her twin brother Jaime Lannister (Nikolaj Coster-Waldau). Jaime shoves Bran out the window to ensure his silence.
When Bran wakes up, he's lost the use of his legs, but has begun to develop magical abilities, including seeing vision. When Theon Greyjoy (Alfie Allen) captures Winterfell, faking Bran's death in the process, he and his brother Rickon (Art Parkinson), simple minded stableboy Hodor (Kristian Narin), and wildling ally Osha (Natalia Tena) flee the castle, where they encounter the Reed siblings, Meera (Ellie Kendrick) and Jojen (Thomas Brodie-Sangster).
Jojen then advises Bran to go beyond the Wall, seeking out the mystical Three-Eyed Raven (Straun Rogers in season 4, and Max Von Sydow in season 6) to help hone his new powers.
Bran then parts ways with Osha and Rickon, joining Hodor and the Reeds on a treacherous quest North. With the help of Sam Tarly (John Bradley), they make it past the Wall, and to the cave of the Three-Eyed Raven. Just as they are about to enter, Bran and his team are attacked by undead wights, and Jojen dies in the process. When Bran finally makes it to the cave and meets the Three-Eyed Raven, he promises that Bran will never walk again, but someday, he'll fly.
This is the last audiences see of Bran until season 6. The show explained its decision by allowing Bran some time to train off-screen, and to allow other characters to catch up to Martin's published works. However, with an eleven episode gap between appearances, casual audiences may rely heavily on the "previously on" to catch them up on Bran's storyline by the time he comes back.

Bran's (nonexistent) role in A Feast for Crows
Game of Thrones season 5 is not the first time Bran sits out of a major A Song of Ice and Fire production. Despite having appeared in every previous book, Bran misses A Feast for Crows entirely. After Bran's final chapter in A Storm of Swords, Martin's third book in the series, he does not reappear until A Dance With Dragons.
However, unlike in the show, Bran is not alone in missing a book. Martin divided his point-of-view characters between the two books. Crows mostly focuses on Cersei, Jaime, Sam, Brienne of Tarth (Gwendoline Christie), and Sansa Stark (Sophie Turner), among others, while Dragons brings Bran, Jon Snow (Kit Harington), Tyrion Lannister (Peter Dinklage), Daenerys Targaryen (Emilia Clarke), and Davos Seaworth (Liam Cunningham), for example, back into the fray.
As such, even the likes of Tyrion and Daenerys, arguably two of the most iconic characters in the entire franchise, end up not appearing in every book.
The difference between Bran's absence in season 5 and from A Feast for Crows is that he stands out as the only character to miss an entire season, whereas in the books, half the main cast isn't in each novel. Bran being the sole leading character not in season 5 both makes it seem like his storyline is less important than the others, and all but gives the audience permission to forget about him and develop stronger attachments to the rest of the cast.
Perhaps this is why Bran's ending as King of Westeros received so much backlash from viewers, since the character with the "best story" probably isn't the only character to just casually leave the series for a season.
For more from the world of Westeros, make sure to stream A Knight of the Seven Kingdoms and House of the Dragon on HBO Max.
