House Clegane is a house of landed knights that holds fealty to House Lannister of Casterly Rock, and are among their primary bannermen. Their lands are southeast of Casterly Rock and include a towerhouse, which is named Clegane's Keep. Their sigil is three dogs on a yellow field.
The first knight of House Clegane was kennelmaster at Casterly Rock until one autumn year when he saved Lord Tytos Lannister from a lioness and lost a leg and three dogs in the effort. As a reward, Tytos gave him lands and a towerhouse and took his son as his squire. The three dogs on the Clegane sigil represent those that died saving Tytos.
The kennelmaster's son, the father of Gregor and Sandor, died in a hunting incident shortly after King Robert Baratheon was crowned. Their sister died young under queer circumstances. Gregor is known for his unspeakable cruelty; this is mirrored in his men, who casually commit atrocities during their campaigns. Sandor was driven away by this behavior, taking service with House Lannister and refusing to take a knight's vows to avoid association with his elder.
During the Sack of King's Landing, Gregor allegedly murdered the infant Prince Aegon Targaryen and Princess Rhaenys before raping and murdering his mother, Princess Elia Martell.
House Clegane sits in Clegane's Keep, located in the Westerlands, southeast of Lannisport. There is a village under the keep. The keep has a fearsome reputation, one that lives up to that of its lord during the War of the Five Kings, Ser Gregor Clegane. It is said that servants disappear unaccountably, and even the dogs are afraid to enter the hall.