From A Wiki of Ice and Fire
Clegane's Keep is the name given to the seat of House Clegane in the Westerlands acording to a semi-canonical sourced. It was given to the first Clegane knight, the kennelmaster at Casterly Rock, who saved Lord Tytos Lannister from a lion and lost a leg in the effort. The keep has a fearsome reputation; one that lives up to that of its lord, Ser Gregor Clegane. It was said that servants disapper unaccountably, and even the dogs were afraid to enter the hall.