Nightsong is a castle in the Stormlands. It is the seat of House Caron, a vassal house holding fealty to House Baratheon of Storm's End. The castle is located south-west of Storm's End near the border with Dorne.
In the books
In the A Song of Ice and Fire novels, Nightsong is a major stronghold of the Dornish Marches. House Caron are known as the "Lords of the Marches", suggesting they may have some superior authority over the other march lords (such as House Dondarrion). Houses Caron and Dondarrion allied together to fight the Vulture King, a bandit lord based in the Red Mountains, some ninety years before the events of the books. Ser Arlen of Pennytree and his squire, the future Ser Duncan the Tall, accompanied this campaign.
In the books, House Caron is effectively destroyed when its last surviving members are killed during the Battle of the Blackwater, resulting in the castle of Nightsong passing to House Foote.