Brightbank is a large fortress / village located in the North, on the western edge of the Wolfswood, located west of Deepwood Motte and south of Sea Dragon Pointe. It is the seat of House Grayburn.
Before being known under the name "Brightbank", this castle existed for a number of years, though it is unknown who originally occupied it. By the time of Aegon's Conquest, it lay abandoned. Following the end of the war, Aegon gave the castle to Gared the Gray, a Westerosi lord who joined up with him early on in the war and became one of his number-one fighters. Gared re-named the castle "Brightbank" and founded House Grayburn.
Brightbank is first seen when Carmine returns there after having fled King's Landing following newly-crowned King Joffrey Baratheon's purge of Stark forces in the city. He meets with its Maester Aderic and William Blackfell (who serves as both Master-at-Arms and Castellan of Brightbank) and explains what happened, who in turn inform him that his father has gone to Winterfell after Robb Stark has called his banners. Carmine then rides off to Winterfell to join him. However, Carmine convinces his father to return to Brightbank, claiming that Brightbank needed him. Hendrick agrees.
In the aftermath of the Red Wedding, a wounded Carmine manages to flee the massacre, but not before his squire, Sammith, is killed. He returns to Brightbank to inform his father of what has happened. Carmine proposes to for a new militant force to finish the job that Robb Stark started.