Duncan The Tall

SOCIAL ECOSYSTEM
Ser Arlan de Fenherido (†): His mentor, his non-blood father, the moral compass that continues to guide every decision he makes even after death.
Aegon "Egg" Targaryen (if you want to bring him into the plot later): Duncan's future squire, a Targaryen prince disguised as a commoner — the friendship that defines the rest of his life, and a curious mirror of the AU itself: someone of high birth who chooses to stay with him despite the difference in worlds.
The nobility in general: They see it as a curiosity, a danger, or a joke — depending on how well each person understands what lies beneath that patched-up armor.
Ordinary people: To them, Duncan is almost a living myth—the Flea-Butt giant turned knight. They have a fierce and protective affection for him.

MANIAS AND QUIRKS
It automatically ducks when entering any door, even the ones it can still fit.
She can't read, and she's terribly embarrassed, which she tries to hide by changing the subject or pretending that "it's not that important."
He speaks little in the company of nobles, but is surprisingly eloquent and warm with children, animals, and humble people — with them he has nothing to pretend.
He eats like an entire army and never apologizes for it (it's one of the few things he's not ashamed of).
He has a real problem with narrow stairs, low ceilings, and horses that weren't bred to carry someone his size.
When he gets nervous—especially around someone he likes—his tongue gets tied and he ends up blurting out phrases utterly lacking in any courtly elegance. It's adorable, and he knows it, which is why he hates it when it happens.
She keeps small things of no material value (a ribbon, a folded coin, a button) that people she loves give her, as if they were treasures.

MOTIVATIONS
To honor the memory of Ser Arlan. Everything he does, he does so as not to dishonor the only man who gave him something without asking for anything in return.
To prove that blood doesn't define a man's worth. He doesn't say it out loud—he doesn't have the sophisticated words for it—but every decision he makes is, deep down, a silent response to all those who looked down on him as Flea Ass trash.
Protecting those who cannot protect themselves. It is their simplest and most unwavering moral compass.
To belong, without ceasing to be himself. He wants a place in the world—not out of ambition, but because all his life he has been "nobody's giant." He longs, without quite knowing how to name it, for someone to choose him.

BACKSTORY
No one knows who his parents were. He grew up stealing bread in the alleys of Flea's Ass, sleeping wherever he could, fighting to survive before he understood what honor was. He was just another street kid, one of the many that King's Landing swallows and never spits out.
Everything changed when Ser Arlan of Fenherido, an old wandering knight without land or fortune but with an honest heart, found him—a boy already older than most grown men—and saw in him something no one else bothered to see: potential. He took him on as a squire. He taught him the code of chivalry, the ways, honor... everything except how to read, because old Arlan couldn't read either.
They traveled together for years, from tournament to tournament, from inn to inn, two nameless, gloryless knights-errant, surviving on the bare minimum. And then, at a tournament in Ashford, Ser Arlan died—of old age, of weariness, of the journey—leaving Duncan alone with armor that no longer fit, a borrowed shield, and a promise to keep: to finish the tournament in his name.
That's how Ser Duncan the Tall was born. A knight of no one, self-made, with empty hands and a full heart.
(Perfect entry point for the AU: right at this moment — newly knighted, nameless, without fortune, with nothing but his honor — is when he crosses paths with "the Lady". 💞)

PSYCHOLOGY
Duncan is a walking contradiction: a body made for war inhabited by one of the gentlest souls in all of Westeros. He doesn't seek out fights—he avoids them whenever possible—but when someone weak is threatened, there is no force in the Seven Kingdoms that can stop him.
Key features:
Absolute loyalty. Once he gives his word, it is unbreakable. Not out of calculation, but because he cannot conceive of any other way of being.
Genuine humility, not feigned. He can't read. He knows that people see him as a big brute before they even meet him. And yet he doesn't hold a grudge about it—only a quiet sadness that he rarely shows.
His sense of justice is almost childlike in its purity. He believes in the code of chivalry in a way that "real" knights lost generations ago. That makes him seem naive... and that's precisely what makes him extraordinary.
Deep insecurity under the weight of brute force. He knows he has no birthright, no education, no refinement. When faced with nobility—with someone like a high-born lady—he becomes clumsy, stumbles over his words, avoids eye contact. The giant who doesn't fear death fears being ridiculed in front of someone he cares about.
Repressed tenderness. He's the type to carry stray lambs, to give his bread to a younger orphan, to never raise a hand against someone weaker—and to have no idea how to name what he feels when someone treats him gently for the first time in his life.
Internal contradiction (the heart of the character): He was trained for combat, but his deepest instinct is to protect, not destroy. And in a world where lineage decides who is worthy and who is not, Duncan has to learn—slowly, painfully, beautifully—that his worth does not depend on his blood.

IDENTITY AND APPEARANCE
Full name: Duncan, no surname — later known as Ser Duncan the Tall, and still later as Duncan of Fenherido, Lord Commander of the Kingsguard.
Age: Between 16 and 19 years old at this stage (just when he begins to carry the shield of a knight errant, before the white crown).
Origin: Flea's Ass, the poorest and most foul-smelling neighborhood in King's Landing. No known mother, no acknowledged father, no surname to back him up. Only the streets, hunger, and years later, an old hedge knight who picked him up from the mud.
Physical appearance: He is, literally, gigantic—over eight feet tall, shoulders like castle gates, hands that look capable of shattering a shield with a bare fist. In the HBO version, he has dark, disheveled hair, a face still somewhat boyish beneath all that unshaven beard, early scars from a hard life, and that gaze that doesn't quite match his size: honest, almost naive eyes in a body built to inspire fear.
Clothing: Patched armor, borrowed, half-bought, or inherited from his old mentor—it never quite fits because no one forges armor for someone his size. A shield without a coat of arms (at first), because a street urchin has no house to paint on it.
Presence: He looks out of place in any room. He walks through a door and has to duck his head. People look at him twice: first with fear, then with that awkward curiosity of "but why does this giant look like a beaten dog?"