A general view of show props at HBO's "Game of Thrones" Season 6 behind the scenes fan event at Hollywood & Highland on December 9, 2016 in Hollywood, California. (Photo by Tasia Wells/WireImage)

With Game of Thrones season 6, episode 6, “Blood of My Blood,” the stakes have changed yet again with the recently revealed actions of the (in)famous “Blackfish.” Who is Blackfish? That would be the nickname of one Brynden Tully, leader of House Tully and a character not seen since season 3. But that answer only tells you about the nickname: Who is Blackfish Tully? Learn more about the character below, and why he may be a deciding factor in future episodes of Game of Thrones season 6.

If you’ve yet to read a Game of Thrones recap (and if not, we’ve got you covered), the most recent episode saw plenty of developments, including Bran apparently being stuck traveling through time until he stopped long enough to be saved by Benjen Stark, Samwell Tarly returning home to his intimidating father, Daenerys preparing the Khalasar for war, and Jaime Lannister being ousted as head of the Kingsguard.

While it may have seemed like a minor detail in comparison to some of the above events, “Blood of My Blood” also saw Walder Frey address his sons, who lost Riverrun to Brynden “the Blackfish” Tully. Riverrun, for the uninformed, is a castle that has primarily served as the base of operations for House Tully over the course of at least 1,000 years, meaning Blackfish’s desire to reclaim it should have been obvious. However, what’s important is how he did it: he managed to bring together an entire army and take the castle by force!

For those who don’t know him—or don’t remember him, given how long he’s been off screen—Brynden Tully is the current head of House Tully following Hoster Tully’s death and Edmure Tully having been taken as a hostage by House Frey following the Red Wedding. The name Blackfish was inadvertently given to Brynden by himself after he commented that he was the “black fish” of the family for wanting to remain a bachelor; the House Tully sigil is a trout, hence why black fish and not the traditional “black sheep.”

The Blackfish was last seen at the end of season 3, just missing out on being another victim of the Red Wedding when he picked the best possible time to use the restroom in what was probably the biggest stroke of luck in Game of Thrones history (in the books, he wasn’t in attendance at the wedding in the first place, having stayed behind to defend Riverrun on the order of Robb Stark).

Known as a skilled combatant, the Blackfish’s reputation allowed him to bring the remaining Tully soldiers back together into a strong enough unit to drive the Freys from Riverrun. This action has of course invited repercussions as Jaime Lannister has made clear his intentions to personally take back the castle from its recently reestablished ruler.

But the events at Riverrun may not be where Brynden “The Blackfish” Tully’s role in the story begins and ends. He is also the great-uncle of Sansa Stark, who recently sent Brienne to Riverrun in hopes of getting her relative to help her and Jon Snow reclaim the North from Ramsay Bolton as part of their apparently season-long journey to rally as many of the Northern houses behind them as they can. We may get the Blackfish’s response as soon as the next episode, season 6, episode 7; however, given the threat of the Lannister forces currently heading for the castle, he may need Sansa and Jon’s help before he has any hope of being able to assist them.