From the announcement:
Fantasy Flight Games is proud to announce the upcoming release of The Wars to Come, an expansion for Game of Thrones: The Iron Throne!
Along with ten new leaders, divided between two new Houses—House Greyjoy and House Martell—The Wars to Come features everything you and your friends need to expand your games of The Iron Throne to seven players. Can you rise above all six of your rivals to claim the Iron Throne? The Wars to Come ensures that you'll not only find yourself confronted by more Houses, but by more of the chaos created by war and your opponent's unpredictable talents.
Additionally, The Wars to Come introduces a deck of twenty-five new allies. These iconic characters root your schemes and politics more firmly in the world of HBO's acclaimed Game of Thrones, even as they permit access to a wide range of new abilities that can dramatically change the shape of a battle—or even the game!