Grand Maester Pycelle
The ancient Grand Maester of the Red Keep, who has advised king after king with much bowing and throat-clearing and rather more cunning than he lets show.
The fuller tale
Pycelle has served on the small council longer than most of its members have been alive, and has survived that long by perfecting the realm's most underrated disguise: uselessness. Donning the Grand Maester's chain young and brilliant, he aged into an institution — the vast beard, the shuffling gait, the throat-clearing preambles that send councils into a coma — and somewhere in those decades the performance and the man quietly merged. The court sees a doddering relic; the relic sees everything. Under the palsied hands and the interminable courtesies operates one of the most consistently partisan men in King's Landing, and the partisanship has never once wavered: through five kings and forty years, Pycelle serves House Lannister.
His loyalty predates the story and repeatedly bends it. It was Pycelle who counseled the Mad King to open the gates to Tywin's army during the sack — a single whisper that delivered King's Landing to the lions — and Pycelle who, by his own eventual confession, let Jon Arryn die of his poisoning rather than cure a man whose investigations threatened Cersei's children. The story's schemers all know what he is: Tyrion, hunting the council's leak, feeds each counselor a different secret and identifies Pycelle when his version reaches Cersei, then has the old man hauled from his bed — beard shorn, dignity confiscated, black cell provided. The realm's oldest servant weeps and pleads and survives even this, restored to his seat by Tywin because a known instrument is worth more than an honest stranger.
The last act finds him outlived by his own methods. With Tywin dead, Pycelle attaches himself to the surviving center of gravity — in the show, that means Cersei, until her disasters teach him better, and his final allegiance goes to the sober regency rebuilding the realm around her. It is the correct call, made one regime too late. Pycelle's whole career argues that in King's Landing survival is a skill distinct from wisdom, practicable for decades by a man with no illusions and no scruples; the tale lets the argument run its full length before submitting its rebuttal.
The page and the screen
The tellings agree on the man and differ on the exposure. The books formalize what the show implies: the Citadel's maesters are meant to serve the realm, and Pycelle's confession to Tyrion — that he has always served House Lannister first, since Tytos's day — lands as institutional scandal, not just personal corruption. His book arc after Tywin's death is fuller: trembling before Cersei's regency, quietly conspiring with Kevan to repair her damage, part of the sober old guard whose competence becomes, fatally, its own provocation. The show also awards him a small parting gift the books withhold — a wordless scene of the shuffling dodderer straightening, mid-corridor, into a hale man once unobserved, the series' confirmation that the senility was always a costume.
Where they stand, season by season
Their fate — if death has found them, it is written here. Open at your peril.
The show: Died in the Red Keep (S6·E10)
The books: Killed by the little birds (ADWD, ch. 73)
The old maester who served five kings and betrayed most of them was lured to Qyburn's cellar and stabbed to death by little birds with little knives — the price of standing between Cersei and her new order.
Both tellings kill him with children's knives, in service of opposite conspiracies. In the show, on the morning of Cersei's trial, one of Qyburn's little birds leads the Grand Maester down into a cellar beneath the Red Keep, where Qyburn waits with something like regret — his former colleague, he explains, is an obstacle to the new order — and the swarm of children closes in with blades while the sept across the city awaits its green fire. In the books the little birds still answer their original master: in the fifth novel's epilogue, Varys's children ambush Pycelle at his own table and stave in his skull, the first course of the double murder that claims Kevan Lannister in the same chambers — the Spider erasing the two men mending the realm his hidden prince needs broken. Either way the end is the same shape: the great survivor of five reigns, who outlasted every purge by seeming harmless, dies at the hands of the only players in King's Landing more invisible than himself.