Maisie Williams and Sophie Turner
Cast members Maisie Williams and Sophie Turner arrive for the season four premiere of the HBO series ''Game of Thrones'' in New York March 18, 2014. Reuters/Lucas Jackson

Known for his role as Mycroft Holmes in the British series "Sherlock," Mark Gatiss is scheduled to reprise his role as Tycho Nestoris in the 5th season of HBO's "Game of Thrones." Playing the representative of the Iron Bank, Gatiss debuted his role in GOT Season 4 "The Laws of God and Men."

Playing a much bigger part in the serie's Season 5, the actor is expected to be back in the GOT set in Croatia next week. His return to the show means that he is set for bigger role now that everyone in Westeros are preparing for the long winter and the impending war to claim the Iron Throne.

Splitting his work between three projects, "Sherlock, "Doctor Who" and "Game of Thrones," the British writer is up for another explosive season on his hit show with Benedict Cumberbatch and Martin Freeman. Gearing up for the show's fourth season, Gatiss revealed that they are building up a good plot that will end to a "darker climax."

Here are the five things to know about Tycho Nestoris, the Iron Banker.

1. The Braavosi banker appeared on the show for the first time when the Iron Bank funded Stannis Baratheon's war against the Lannisters, who is also in heavy debt with the bank. Feared by many, the Iron Bank is the worst enemy any ruler can have as they can fund debtor's enemy if the payments are not paid on time.

2. Representing the biggest bank in the Seven Kingdoms, Gatiss's role maybe small compared to other characters, but he is going to make a huge impact in the future seasons of the show.

3. In George R.R. Martin's book "A Dance With Dragons," Jon Snow negotiated with him to use a few of his ships to get food and supplies for the Nights's Watch. In return for the loan, Snow gave him a guide on how to reach Stannis for the Iron banker to collect his debts.

4. In Martin's upcoming book, "The Winds of Winters," Nestoris signed an agreement with Stannis as he acknowledged the Iron Throne's debt and granted him with another loan.

5. Tycho will have a chance to meet Arya Stark when Stannis ordered Ser Justin Massey to escort them back to The Wall.