House Darklyn was once among the proudest houses of the crownlands, seated at the Dun Fort in Duskendale upon the narrow sea. Before the coming of Aegon the Conqueror the Darklyns reigned as petty kings, and in the centuries before King's Landing grew to greatness their walled town was the busiest port on the Blackwater coast, its harbor thick with the cog and the carrack. Even after they set aside their crowns and bent the knee, the lords of Duskendale remained a power among the small lords of the narrow sea, jealous of the trade that the rise of the Targaryen city slowly drew away from their wharves. Their arms were fusily black and gold, charged with a red tierce that bore seven white shields, one for each of the seven Darklyns who wore the white cloak of the Kingsguard, more than any other house has given.
The house met its end in 277 AC in the catastrophe remembered as the Defiance of Duskendale. Lord Denys Darklyn, by the chronicles goaded by his Myrish wife Serala, called the Lace Serpent, defied the Iron Throne over the matter of a royal charter and, when King Aerys II Targaryen came in person to settle the dispute, seized his sovereign and held him captive within the Dun Fort for half a year. Lord Tywin Lannister brought the royal host to lay siege, but it was Ser Barristan Selmy who slipped inside the walls by night and freed the king. Aerys took a terrible vengeance: he put Lord Denys and the whole of House Darklyn to the sword, along with their sworn House Hollard, and so an ancient line was extinguished root and branch, sparing only a boy, Dontos Hollard, at Ser Barristan's plea. House Rykker was granted Duskendale and the Dun Fort in the Darklyns' place.