Maester Aemon
The blind old maester of Castle Black, a hundred years in service on the Wall — and, though few now remember it, a son of a Targaryen king who once stood near the throne.
A soul of House Targaryen, born at King's Landing, sworn to The Night's Watch.
The fuller tale
Season One
Blind, past ninety, and content to be thought of as just the old man who tends the ravens, though everyone at Castle Black who bothers to ask knows Aemon Targaryen chose the Wall over a throne two civil wars ago. He takes an interest in Jon Snow that has nothing to do with sympathy for another man's bastard and everything to do with recognizing the particular loneliness of a boy who has never fully belonged anywhere. When word reaches the Wall that Ned Stark is dead and Robb has called the banners, Aemon is the one who talks Jon out of riding south, laying out — gently, and from experience — exactly what it costs a man to choose duty over blood.
Season Three
Castle Black spends the season waiting on news from beyond the Wall, most of it bad, until Sam Tarly staggers up to the gate in the last hours of the year with Gilly and Craster's infant son and nothing left in him to argue with a guard. Aemon is the one who cuts through the Watch's centuries-old rule against harboring wildlings and orders the gate opened without needing to see who is standing on the other side of it, and it is Aemon, not the men with working eyes, who understands first exactly what has just arrived at the Wall.
Season Four
With most of the Watch's fighting strength stripped for the Wall's defense, Aemon becomes the closest thing Castle Black has to a war council chief who never leaves his chair. He dictates ravens sent out to every keep and holdfast in the Seven Kingdoms warning that the wildling army is coming and the Wall will not hold itself, aware from three hundred years of the Watch's history exactly how many of those letters will actually be answered. When the attack comes he stays where he is most useful, out of the fighting and close to a bell that needs ringing, ancient and steady while younger men lose their nerve around him.
Season Five
Jon sends him south with Sam and Gilly and the baby, ostensibly so Sam can begin training at the Citadel, mostly because Aemon is too old and Castle Black too dangerous for him to stay any longer. A storm blows their ship off course to Braavos instead of Oldtown, and it is there, in a stranger's house, that his age finally catches him. He dies with Sam and Gilly beside him, drifting back to a boyhood nobody at the Wall ever knew he had, mistaking the moment for a much earlier one and calling for a brother the rest of the world remembers only as a king.
How it ends for them
On the screen. Died of great age (S5·E7)
Aemon Targaryen, maester of the Watch for sixty-seven years, died old and blind and gentle in his bed at Castle Black, laughing with his brother Egg in his last dreams. 'And now his watch is ended.'
On the page. Died at sea (AFFC, ch. 36)
Sam carried the blind old maester south to save him from Melisandre's fires, and the sea's chill caught him past Braavos. He died aboard the Cinnamon Wind at a hundred and two, dreaming of his brother Egg and murmuring of a dragon with three heads.
On screen he dies as he lived, in his bed at Castle Black, ancient past reckoning, laughing softly with people sixty years dead — “Egg, I dreamed that I was old” — while Sam and Gilly keep the vigil. The Watch burns him with full honors, and even Alliser Thorne’s eulogy is gentle: a hundred years of service ended without an enemy in the world.
The books give him a sailor’s death instead. Carried south to escape the red woman, he weakens past Braavos, and at one hundred and two years old dies aboard the Cinnamon Wind, tended by Sam and Gilly, dreaming of his brother and murmuring about dragons — the last work of his life, the riddle of the three heads, spilling out with his final breaths. The crew commits him to the sea. In both tellings the same words close the account, and nowhere in the saga do they land harder: and now his watch is ended.
Their chapters, book by book
A Game of Thrones 1 chapter that name them
A Storm of Swords 1 chapter that name them
A Feast for Crows 3 chapters that name them
Where the page and the screen part
The show keeps Aemon at Castle Black to the end; the books send him on one last journey. When Melisandre arrives hunting king’s blood, Sam smuggles the old man south by sea to keep him out of her fires — through Braavos, where the news of Daenerys reaches him, and out onto the long water aboard the Cinnamon Wind. Dying, he burns bright: it is book-Aemon who works out that the prophecy of the prince that was promised may point at Daenerys, that the dragon must have three heads, and who charges Sam to reach the Citadel and send help to her. The show, having no Citadel voyage to give him, folds his farewells into Castle Black and hands his prophetic function to other mouths. Both tellings agree on the essentials: the refused crown, the blindness, Egg, and a death gentler than any other Targaryen is granted.
Their journey
Where the two tellings send them to the same place the road runs whole; where they part, the screen keeps the left and the books the right.