Arthur Dayne
The Sword of the Morning: a knight of the Kingsguard in the last Targaryen reign, who carried the pale greatsword Dawn and is named by everyone who ever crossed blades with him as the finest sword of his age.
A soul born at Starfall.
The fuller tale
Their story
House Dayne of Starfall sits on the Torentine at the western edge of Dorne, an old line with one peculiar possession. Dawn is a greatsword, pale as milkglass, and it is not Valyrian steel — it is said to have been forged from the heart of a fallen star, and it is not inherited in the ordinary way. Each generation the Daynes give it only to a knight of their own blood they judge worthy of carrying it, and he is called the Sword of the Morning. In most generations there is nobody. In his there was.
He was raised to the Kingsguard young, and by the common judgement of every man qualified to judge — including two who had every reason in the world to prefer a different answer — he was the finest knight of his age and probably of several. Not merely fast: fast and enormous at the same time, which is a combination the training yards turn out about twice a century. The men he beat did not complain about it afterwards. They talked about it for the rest of their lives.
The other half of him is the half the songs usually leave out, because it is harder to set to music. He was decent. He hunted down the Kingswood Brotherhood, outlaws who had made the royal forest impassable for years, and when he had broken them he went back and did something about the grievances that had filled their ranks in the first place — which no other commander sent against them had thought worth the trouble. Knights who are both the best and the kindest are a thing the singers invented; occasionally the world produces one anyway.
How it ends for them
Fell at a tower in the Dornish marches, before the story — before this story begins.
He died at a tower in the Dornish marches — three Kingsguard against seven northmen, in a fight only two men walked away from. Ned Stark and Howland Reed came down off that hill; nobody else did.
The question that fight leaves behind is the loudest unanswered question in the whole backstory, and it is not about swordsmanship. Three white cloaks, including the finest knight in the Seven Kingdoms, were standing guard over a tower in the far south while their king was besieged, his heir was riding to the Trident, and the dynasty they had sworn their lives to was being pulled down stone by stone. They were not lost. They were not late. They were exactly where they had been ordered to be, and they would not leave, and they said so.
The answer is upstairs, and Ned Stark carried it out of that room and did not tell his wife, his king or his children for the rest of his life.
Their chapters, book by book
Where the page and the screen part
The screen gives him one scene and makes it count: a fight outside a tower in the Dornish marches, remembered decades later by a man who was there, with two swords instead of one and an ending that the rememberer has clearly been editing in his own head ever since. The books never show him alive at all. Every word we have about him is somebody's recollection, and the recollections are unanimous, which for this author is itself remarkable.