House Darklyn

The extinguished lords of Duskendale, once kings of the narrow sea, undone in a single stroke by the folly of the Defiance of Duskendale.

The fuller tale

Before the Targaryens, the Darklyns were kings at Duskendale, the old port town on the Bay of Crabs, and even as lords under the dragon they remained proud, ancient, and rich on the trade that passed their walls. All of it ended in the reign of Aerys the Second, in the disaster the histories call the Defiance of Duskendale.

Lord Denys Darklyn, chafing at royal taxes, seized the person of the king himself when Aerys came to hear his grievance, and held him captive for half a year. When Ser Barristan Selmy at last rescued the king by stealth, Aerys took a terrible revenge: House Darklyn was extinguished root and branch, every man, woman and child of the line put to death. The town passed to other hands, and the king's captivity is widely blamed for tipping Aerys the rest of the way into madness.