Riverrun is a strong three-sided castle, although not especially large, situated at the point where the Tumblestone and Red Fork rivers meet. A moat on the third side of the castle can be flooded to leave it practically unassailable. The Tullys were never kings but were the chief leaders of the rebel riverlords who deserted Harren the Black and joined Aegon the Conqueror and so were rewarded with overlordship of the lands watered by the Trident. Their motto is, “Family, Duty, Honor.”
Lord Hoster is an old man, afflicited with an illness which has left him a bed-ridden invalid. His son and heir is Ser Edmure, a proud, hot-tempered, short-sighted man. Lord Tully joined the rebellion against Aerys, in part because Brandon Stark and his lord father Rickard had arranged a marriage with Lord Tully’s eldest daughter Catelyn before their deaths. Eddard Stark fulfilled the marriage contract and Lord Tully’s younger daughter Lysa was wed to Lord Jon Arryn.
After the Lannisters sparked a conflict in retribution for Lady Catelyn Stark’s kidnapping of Tyrion Lannister, Ser Jaime Lannister smashed the Tully host beneath the Golden Tooth, captured Ser Edmure, and laid siege to Riverrun. Lord Robb Stark, through a brilliant maneuver, captured the Kingslayer and broke the siege with an ambitious surprise attack lead by Ser Brynden Tully, Lord Hoster’s brother. There at Riverrun, the northerners and the riverlords proclaimed him King of the North and the Riverlands.
Afterwards, Edmure had repelled a major Lannister attack on the Red Fork which aimed to get at the westerlands to stop King Robb’s nearly unopposed raiding. However, Robb’s return with a Westerling bride began to bring everything to disaster. Lord Hoster passed away before arrangements were made for Lord Edmure to marry Roslin Frey, one of Lord Frey’s many daughters. Edmure wedded and bedded the girl, only to be taken prisoner while many others were slain in the Red Wedding, including Lady Catelyn and King Robb.
Riverrun has been granted to Ser Emmon Frey and his wife Lady Genna of House Lannister, to complete the shift of power in the riverlands away from the Tullys when Petyr Baelish was named overlord of the Trident after the battle of the Blackwater. Riverrun remains in the hands of Ser Brynden Tully, but with Edmure a hostage it is doubtful that resistance will last long.