Qyburn

Qyburn is a recurring character in the third, fourth and fifth seasons. He is portrayed by Anton Lesser and debuts in "Valar Dohaeris". He is one of the prisoners at Harrenhal left for dead by Ser Gregor Clegane.

Background
Qyburn is a former maester of the Citadel. He was stripped of his chain by the Archmaesters for engaging in forbidden experiments.

Season 3
Qyburn is among the Northern and Riverlands prisoners at Harrenhal when Ser Gregor Clegane abandons the castle and has all captives put to the sword. Qyburn, however, survives the injury at his throat and awakens when the castle is taken by the Northern army. After he wakes, he identifies himself to Robb Stark while Talisa Stark tends to his wound. After Robb leaves Harrenhal, Qyburn stays behind, serving under Lord Roose Bolton. He tends to Ser Jaime Lannister's badly infected stump, result of Locke removing his right hand. During this time, Jaime notices that Qyburn is not a Maester, because he isn't wearing a maester's chain of office. Qyburn acknowledges this, explaining that he was stripped of his chain by the Citadel and thrown out of the Order of Maesters for conducting experiments which they felt were too "bold". Qyburn initially intends to amputate part of Jaime's arm, but Jaime begs him not to, even threatening to kill him. Qyburn agrees to instead resort to removing the infected flesh, warning that the process will be painful and likely require milk of the poppy, but Jaime, worrying that Qyburn may still amputate his arm, refuses. Qyburn straps Jaime's arm to the chair and starts the painful procedure.

Qyburn volunteers to join the party escorting Jaime back to King's Landing. Lord Bolton theorizes that the former Maester is doing so in the hopes that Tywin Lannister will force the Citadel to restore his chain. After leaving Harrenhal, when Qyburn checks on Jaime's healing stump, Jaime notes that Qyburn's work is far superior to that of Grand Maester Pycelle and asks why the Citadel removed his chain. Qyburn tells him that it was for performing experiments on living humans in order to learn more about their anatomy, and justifies his actions by noting that he used the information he gleaned from them to save lives. Jaime briefly mocks Qyburn, who shoots back at Jaime for the countless lives he's taken, though Jaime notes that he saved the population of King's Landing from the Mad King. When Jaime then asks Qyburn about Brienne, he states that her father offered Locke a fair ransom of three hundred Gold Dragons, which Locke refused to accept due to a previous lie of Jaime's that Brienne came from a wealthier family than she really did. Qyburn tells Jaime that she will most likely serve as entertainment for Locke and his men that night, and be killed thereafter. Qyburn then accompanies Jaime and Steelshanks to Harrenhal when Jaime blackmails Steelshanks into helping him rescue Brienne.

Qyburn is still with Jaime and Brienne when they finally reach King's Landing.

Season 4
Qyburn has a solid gold hand forged for Jaime and personally fits it on him. Cersei voices her gratitude to Qyburn, who then ingratiates himself with the Queen by aiding her in other matters.

After Gregor Clegane is seriously wounded during his fight against Oberyn Martell, Qyburn and Pycelle theorize that Oberyn coated his spear in Manticore venom, causing Clegane's wounds to fester and leave him in agony. Pycelle concludes to Cersei that Clegane is likely doomed, but Qyburn opines that he may be able to save him using more unorthodox means (even though Clegane once nearly killed him in Harrenhal). Pycelle snorts that Qyburn is not even a Maester, and reminds Cersei that he was expelled from the Citadel for conducting "dangerous" and "unnatural" experiments. Cersei, remembering Qyburn's success with Jaime's stump, responds by dismissing Pycelle from his duties - and his laboratory. Cersei then gives Qyburn permission to do anything he can to save Clegane, and to come to her should he need anything. Qyburn warns the Queen that the process he intends to put Ser Gregor through may "change him", but when she is satisfied that it will not affect his strength, she instructs Qyburn to carry on.

Quotes
"The only way to treat disease is to understand disease."

- Qyburn

"Qyburn? Deplorable man. Brought shame on the Citadel with his repugnant experiments."

- Grand Maester Pycelle

In the books
In the A Song of Ice and Fire novels, Qyburn is a former maester who acts as a healer in the sellsword company known as the Brave Companions. Qyburn never met Robb Stark, nor was he imprisoned while staying at Harrenhal, and he never met Gregor Clegane until after the latter's fight with Oberyn Martell.

According to Gendry, Qyburn is rumored to practice black sorcery and necromancy.

Qyburn treats Jaime's festering stump as in the TV series, but Jaime's main reason for refusing milk of the poppy during the process is he does not trust Qyburn not to amputate his whole arm.

When treating Gregor Clegane, Qyburn theorizes that Oberyn had adulterated the manticore venom on his spear with sorcery; thickening it in order to slow it's progress through the veins towards the heart, dragging out Gregor's agony.