Tycho Nestoris is a representative of the Iron Bank of Braavos. He is a rational man, more interested in numbers than in words, reasoning that the former are less likely to deceive than the latter.
Shortly after Tommen Baratheon's coronation, Tycho and two of his colleagues receive Stannis Baratheon and his Hand, Ser Davos Seaworth, who ask them to fund their continuing campaign in Westeros. Tycho points out their weak position and is ready to dismiss them when Ser Davos speaks up, relating how he came into Stannis' service, how the latter is a just man who keeps his word, and how he is the best chance for the Iron Bank to get its money back upon the chaos that would follow the death of the elderly Tywin Lannister. This seems to convince the banker and his colleagues, as they agree to fund Stannis.
Tycho receives Mace Tyrell when the latter arrives in Braavos to renegotiate the kingdom's terms with the Iron Bank. Though polite, Tycho seems to dislike Tyrell, whose bumbleness clashes with Tycho's polite dignity. On the way to the bank, Mace offers him fine wines from the Arbor as a token of esteem but Tycho politely declines. After negotiating with Mace for some time, Tycho leads his guest outside to bid him farewell, but Mace keeps talking, stating that singing is a skill that anyone can learn. To prove that, he immediately starts singing a song, much to Tychos disapproval.
A banker with the iron Bank of Braavosa, Tycho Nestoris is very aware of the political situation in Westeros.