Everything you need to know about the Iron Bank of Braavos, which will be important on 'Game of Thrones' next Sunday

Sunday's episode of "Game of Thrones" ended with an unexpected turn. The Lannister army, led by Jaime, abandoned its home of Casterly Rock and took Highgarden, while the Unsullied fought a small contingent of Lannisters.

In taking Highgarden, the Tyrell stronghold, Cersei manages to completely erase the Tyrell bloodline from existence.

While it might seem like an act of revenge on Olenna and a clever battle strategy at first, it's a lot more than that if you think about what happened earlier in the episode. Tycho Nestoris, a representative from the Iron Bank of Braavos, shows up in King's Landing to discuss the crown's massive debts with Cersei. And it looks like Cersei's plan to take Highgarden has something to do with the Iron Bank.

But what exactly is the Iron Bank of Braavos, and how influential is their power in the events to come? Find out below: