Castle Darry is an old but small castle located in The Riverlands and is the seat of House Darry. It's lord at the start of the books is Ser Raymun Darry, though by A Feast for Crows it is in the possession of Lord Lancel Lannister.
The location of Castle Darry is not really specified. Whilst it is said that it is south of the River Trident in the A Song of Ice and Fire novels, in the World of A Song of Ice and Fire book it is meant to be to the North of Lord Harroway's Town.
House Darry used to be amongst the most powerful houses of the Riverlands, and amongst the most powerful vassals of House Tully, but their influence declined after the Darry's sided with House Targaryen during Robert's Rebellion.
A Game of ThronesEdit
Castle Darry is visited by the entourage of Robert Baratheon on the way to Winterfell. During the stay Tyrion Lannister explores and finds tapestries depicting the successes of the Targaryens, showing that they are still loyal to their previous kings.
On their way back to King's Landing the group have to stop at Castle Darry, after Arya Stark goes missing. Castle Darry is used as the base of operations for the search operation. Castle Darry is where Arya is later put on trial before Robert for assaulting Prince Joffrey I Baratheon. As a result of this the direwolf of Sansa Stark, Lady, is killed by Eddard Stark.
A Clash of KingsEdit
Castle Darry is taken by House Lannister shortly after the outbreak of the War of the Five Kings. The Lord of Castle Darry is killed by Ser Gregor Clegane, meaning it passes into the hands of Lord Lyman Darry. Lyman leads an attack to retake the Castle, but they only hold it for a fortnight before Gregor retakes it and puts the entire castle to the sword, including the young Lord Lyman.
Ser Helman Tallhart retakes the castle from Gregor and is commanded by Lord Roose Bolton to put the entire garrison to the sword and burn it to the ground. The castle of Darry is granted to Lancel Lannister by Joffrey Baratheon.
A Feast for CrowsEdit
Outlaws occupy the castle after the departure of the northmen. Ser Kevan Lannister and Ser Harwyn Plumm ride out to rid the castle of the infestation, clearing it for Kevan's son, Lancel. Lancel is married to Amerei Frey, daughter of Merrett Frey and Mariya Darry, securing his control of the lands that are now repopulated.
Ser Jaime Lannister revisits Castle Darry on his way to Riverrun. He feasts with Amerei and Mariya, and notes that Amerei seems to have some feelings for Ser Harwyn. He duels with Ser Ilyn Payne in the Godswood, confessing that he had sex with his sister, Cersei Lannister, in the bed of Ser Raymun Darry on the way to Winterfell.