House Durrandon of Storm's End was the line of the Storm Kings, founded in the Age of Heroes by Durran Godsgrief, who is said to have raised Storm's End itself and given his line both its royal seat and its royal name; tradition long held that every Storm King's firstborn son and heir be named Durran in his memory. From Durran Godsgrief the Durrandons took the crowned black stag on gold as their sigil and Ours is the Fury as their words, both later carried into House Baratheon by right of blood and marriage.
At the height of their power the Storm Kings ruled the whole eastern reach of Westeros, from Cape Wrath to the Bay of Crabs, and for a time held the riverlands as well, wrested from House Teague, though the rivermen chafed under Durrandon rule and many rose against King Arrec Durrandon to join Harwyn Hardhand of House Hoare when he claimed the Trident. Later kings warred with the invading Andals for generations, some resisting, some intermarrying, until King Ormund III forsook the old gods for the Faith of the Seven, and other Durrandons made war on Dorne in turn, Durran the Third twice invading the Dornish only to be turned back by Nymeria.
By the time of Aegon's Conquest, the Storm Kings had long been in decline, squeezed by the Kings of the Reach in the west, Harren Hoare's dominion in the riverlands, and the ever-present threat of Dorne to the south. King Argilac Durrandon, called the Arrogant, held the throne in his old age when Aegon Targaryen came, and it was Orys Baratheon, Aegon's general and rumored bastard brother, who slew Argilac in the Last Storm and ended the Durrandon line as a ruling house. Orys wed Argilac's daughter and heir, Argella Durrandon, and took up her family's sigil, words, and seat as his own, founding House Baratheon of Storm's End with Durrandon blood in its veins.