Geography:

The Rills are a region of the North, ruled by House Ryswell. The Rills are west of the Barrowlands, north of Blazewater Bay, east of the Stony Shore, and south of the Wolfswood.

The Rills are a largely flat land containing hills, lakes, rivers, streams, and brooks. Herds of horses can be found in the Rills. Because of House Ryswell's sigil and House Ryder's name it can be assumed that horses are an integral part of the culture and economy of the Rills.

The Ryswells rule from a keep in the Rills. Rillwater Crossing (also called Glenmore Keep) is a keep in the northern Rills, ruled by House Glenmore. Lord Rodrik Ryswell's sons and cousins are bannermen to him.

History:

After the Long Night, the Rills were ruled by the First Men Kings of House Ryder. The Ryders eventually submitted to House Stark. During his reign, King Theon Stark put down a rebellion in the Rills.

It is unknown what caused House Ryder to be supplanted by House Ryswell, but the failed rebellion may have something to do with it.

In the story of the Seventy-Nine Sentinels, Lord Ryswell's youngest son led a group of Night's Watch deserters to ride into the Rills, hoping to find shelter and aid at his father's keep. Lord Ryswell instead captured them and returned them to the Nightfort.

During his fostering at Barrowton, Brandon Stark, the heir to Winterfell, spent most of his time riding in the Rills, which he enjoyed. There he met Barbrey Ryswell, whom he had a short-lived affair with. When Barbrey's husband, Lord Willam Dustin, was marching off to Robert's Rebellion, she gave a great red stallion, the pride of Lord Rodrik's herds.

Recent events:

Lord Roose Bolton leaves spearmen from the Rills to defend the fords of the Trident.

Maester Aemon sends a raven from Castle Black to the Rills, pleading for aid against Mance Rayder's army.

The Ryswells lead men from the Rills in attacking the Ironborn at the Fever River, and besieging the Ironborn in Moat Cailin.