Warning: This article contains spoilers from the A Song of Ice and Fire book series. Click away now if you don't want to know!
Tycho is a representative from the Iron Bank of Braavos, one of the Free Cities of Essos. In the fifth book in A Song of Ice and Fire, Tycho shows up at the Wall to meet with Stannis (who himself hangs out at the Wall next season) to negotiate the repaying of the Iron Throne’s debt to the Iron Bank.
Apparently, the Iron Throne owes a ton of money to the Iron Bank — something that has been brought up by Tywin this season. The debt was being repaid with regularity during King Robert’s reign. However, by this point in the books Cersei is in charge, and the account has gone delinquent. It’s Tycho’s hope that Stannis will make for a better client. If Stannis agrees to repay them, then Tycho is willing to lend him more money to help him actually secure the throne. Only problem is, when Tycho shows up at the Wall, Stannis is no longer there. He’s taken off to battle the Boltons at Winterfell, so Jon Snow uses the opportunity to get a nice loan for the Night’s Watch.
If none of this is making any sense to you, that’s OK. A lot happens in the books before Tycho comes into play. It looks like the show is changing this plotline up anyway, having Stannis go to Tycho to ask for money instead of the other way around. That said, we can probably expect the Iron Bank to back Stannis if he can convinced them that a) he can take the throne, and b) he'd be more reliable when it comes to paying them back.
Are you excited to meet this character? Sound off in the comments below!