A street orphan of Flea Bottom who never knew his parents and grew an inch shy of seven feet tall by the time he came to manhood. As a boy of five or six he was found chasing a pig through King's Landing by Ser Arlan of Pennytree, a hedge knight who had just lost his squire Roger of Pennytree at the Redgrass Field, and Arlan took him on and gave him the road for a home. For more than a dozen years they wandered Westeros together, the old man and the lunk: Highgarden in the year of Lord Leo Tyrell's hospitality, the halls of Lord Florent for half a year, Lord Dondarrion's hunt for the Vulture King in the Dornish Marches, Lannisport and the Prince's Pass in the company of a Dornish merchant, every road but the one north to the Wall, where Dunk had once hoped to find some tall old man who might be his father. Arlan taught him the lance and the longsword, and the boy, who was better with an axe or a mace than either and slow as an aurochs by Arlan's own reckoning, listened and remembered.
In 209 AC, on the way to a tourney at Ashford Meadow, Arlan died of a chill on the road, and Duncan buried him under a tree and rode on to enter the lists in his stead as Ser Duncan the Tall, knighted, or so he told Plummer the steward, by the old man before his death. At his camp that night a bald boy of nine fell in beside him and would not be put off, and called him Ser Duncan because Dunk was no name for a knight, and took the name Egg in turn; thus the prince Aegon and the hedge knight of Flea Bottom came to be Dunk and Egg. At Ashford he paid a Pentoshi puppeteer named Tanselle to paint a sunset and an elm and a green falling star on his shield, defended her from Prince Aerion Brightflame in the lists, and was hauled to the castle by Prince Maekar for laying hands on the blood royal. To save him from the headsman, Prince Baelor Breakspear demanded a trial of seven and took the field at his side with six others, only to be struck down by his own brother's mace before the trial was finished. Aerion was forced to yield to Duncan, who had bested him with his strength and the rough fighting he had learned in the alleys, and the boy Egg's father gave him his son to squire for as the price of the prince he had lost.
For more than twenty years thereafter Duncan rode the Seven Kingdoms with Egg at his stirrup. They crossed the Prince's Pass into Dorne where Duncan insulted Lady Cassella Vaith, the first highborn woman he had ever met, took ship at Planky Town for Oldtown aboard the White Lady where Egg's brother Aemon measured him an inch short of seven feet, and outran the Great Spring Sickness on the back of a mule called Maester. They served the broken landed knight Eustace Osgrey at Standfast against the widow Rohanne Webber of Coldmoat, and Duncan slew her castellan Ser Lucas Longinch in a trial by combat in a stream that nearly drowned him, took a kiss and a length of red braid from the Red Widow before he rode on, and carried a fresh dagger scar on his cheek for the rest of his life. At the wedding tourney at Whitewalls he rode as a mystery knight beneath a hanged man's sigil, was warned away by John the Fiddler who turned out to be Daemon II Blackfyre, threw Alyn Cockshaw down a well, slew Ser Tommard Heddle in the sept, and broke the Second Blackfyre Rebellion before it had begun when Lord Brynden Rivers and his loyalist host rode in at dawn.
The white cloak came to him at last in the reign of his squire. By 236 AC he wore it as a Sworn Brother of the Kingsguard, and in that same year he personally slew Daemon III Blackfyre in the Fourth Blackfyre Rebellion. When Lord Lyonel Baratheon, the Laughing Storm, renounced his fealty in 239 AC after Prince Duncan, namesake and firstborn son of Aegon V, broke his betrothal to wed a commonborn girl called Jenny of Oldstones, Ser Duncan stood as the king's champion and bested Lyonel in trial by combat, ending the rebellion in an afternoon. He rose to Lord Commander, escorted Egg's brother Maester Aemon to Eastwatch-by-the-Sea in 233 AC at the king's insistence, and in 253 AC, by then white-bearded and old, rode in the winter tourney at King's Landing where a boy of sixteen named Barristan Selmy unhorsed him. In 259 AC he went with his king into the fire at Summerhall, where, by the few accounts that survive, his valor saved some of the survivors from the great burning that consumed king and prince and Lord Commander alike.
He left behind at least one child of unknown line, a shield with his sunset arms that came in time to the armory of Tarth, and the boy who had once been Egg, then was a king, and at the end was ashes beside him.