Warning: Contains spoilers from Game of Thrones Season 6
In Game of Thrones Season 6 Episode 8, we saw that Brienne of Tarth met Jaime Lannister and tried to negotiate a deal with him. The deal was that Brienne would try and persuade Blackfish to surrender the castle to Jaime Lannister who in turn would allow them to ride north unscathed.
Brienne was sent to Riverrun by Sansa Stark to seek support from Blackfish in the upcoming Battle of Bastards between Jon Snow and Ramsay Bolton. Sansa knew that the current strength of their army is not enough to beat the Boltons in the battle and thus was seeking support from each and every House that has ever stood with the Starks.
Blackfish, initially, did not trust Brienne and was not ready to believe what she said about the upcoming battle. But Brienne somehow convinced him to have a look at the letter that Sansa wrote to him. While reading the letter, Blackfish said, “She’s exactly like her mother.” Why did he say that? We never got to know the contents of the letter but recently, HBO released a copy of that very same letter. Here is the letter that Brienne delivered to Blackfish on behalf of Sansa Stark.