When Aegon Targaryen set out to conquer the Seven Kingdoms, he first sought peace with Argilac Durrandon, the aging Storm King, offering to seal an alliance by wedding his own commander and rumored half-brother Orys Baratheon to Argilac's daughter Argella. But Argilac the Arrogant took the offer of a bastard's hand as an insult, and sent the envoy back to Dragonstone with the man's hands hacked off in a box, bidding Aegon give those to his baseborn friend instead. So began the war in the stormlands, and Aegon gave the storm king's answer to Orys Baratheon to repay.
Argilac marched north to meet the Targaryen host and give battle before it could reach Storm's End, and the two armies came together amid a howling tempest that the singers ever after called the Last Storm. Through driving rain and rising wind the fighting raged, and the storm lords charged again and again against Orys's line. In the end Argilac himself, old but unbowed, cut his way to the Baratheon host and there met Orys Baratheon blade to blade, and was slain. With their king dead the storm lords broke, and the last of the Durrandon kings, who had ruled the stormlands for thousands of years since Durran Godsgrief, was no more.
Argella Durrandon barred the gates of Storm's End and declared herself the Storm Queen, but her own garrison had no wish to burn for a lost cause; they raised a peace banner, bound their lady in chains, and delivered her naked to Orys Baratheon's tent. Orys, it is written, treated her with courtesy, clothing her with his own cloak and later taking her to wife. He claimed Storm's End and the lands of the Durrandon as his own, and took for his house the crowned stag and the words of the storm kings, so that House Baratheon rose in the place of the line it had unmade.