He is one of the prisoners at Harrenhal left for dead by Ser Gregor Clegane.
Qyburn is a former maester of the Citadel. He was stripped of his chain by the Archmaesters for engaging in forbidden experiments.
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 Stark left Harrenhal, Qyburn stayed behind serving under Lord Roose Bolton. He tended to Ser Jaime Lannister's badly infected stump. During this 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 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, Qyburn informs Jaime that the Citadel removed his maester's chain for performing experiments on living humans in order to learn more about their anatomy. He justifies this by noting that he used the information he gleaned from them to save lives. 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 the two arrive at King's Landing.
Qyburn assists with the fitting of Jaime's new golden hand, at Cersei's request, and 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 Maester Pycelle theorize that Oberyn coated his spear in Manticore venom, causing Clegane's wounds to fester and leave him in agony. Pycelle advises Cersei that Clegane is doomed, but Qyburn opines that he may be able to save him using more unorthodox means. 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 responds by dismissing Pycelle from his duties - and his laboratory. 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.
Qyburn is at Cersei's side when she confirms that a head brought to her by two bounty hunters does not belong to Tyrion Lannister. Qyburn asks for the head for use in his research. Later on, at a meeting of the Small Council, Cersei appoints Qyburn as the new Master of Whisperers to replace Varys. Grand Maester Pycelle protests vehemently given Qyburn's outcast status, and Kevan Lannister denounces Qyburn as a sycophant and Cersei as a power-grabber
Qyburn is present at a Small Council meeting when the High Septon demands the execution of the High Sparrow after his followers attack him. Qyburn informs the Council that the High Septon had been at Littlefinger's brothel. Later, Qyburn kills a rat as part of an experiment when Cersei enters his laboratory, giving him a message that she wants sent to Petyr Baelish. She also asks him about the state of his work, while glancing at Gregor Clegane's covered body, and Qyburn assures her it is going very well, though there is still a way to go. Soon after Cersei leaves, as Qyburn writes, Gregor begins shaking under the blanket, but Qyburn shushes him calmly
Qyburn is at the meeting of the Small Council when Mace Tyrell departs to negotiate the crown's debt with the Iron Bank of Braavos
Qyburn visits Cersei while she is held prisoner by the High Sparrow, informing her that Grand Maester Pycelle has sent for Kevan Lannister to serve as Hand of the King. He also informs her that King Tommen has become despondent following Cersei's arrest, and that he refuses to eat or see anyone. Finally, just before leaving her, he informs her that "the work continues," presumably referring to his experiments on Ser Gregor Clegane.
After Cersei enters the Red Keep following her walk of atonement, he hastily throws a cloak over her naked body after rushing to her side. He then speaks to Cersei softy and reassuringly as he embraces her, attempting to soothe her. Pycelle looks upon the scene with disgust. Qyburn remarks upon her poor state and bleeding feet. Qyburn then introduces the "newest member of the kingsguard," the 7-8 foot tall abomination he has been working on. At his behest, the golden knight picks her up and they walk away together, further into the Red Keep so Qyburn can clean her up and treat her wounds.
In his laboratory, Qyburn continues to serve as Master of Whisperers by bribing a group of Varys' little birds into his service with boxes of sweets. When Jamie and Cersei arrive accompanied by Gregor Clegane, the children are unnerved by the Mountain, though Qyburn promises them Clegane is a friend. As part of her revenge, Cersei asks Qyburn to bribe more of Varys' spies stationed in the other kingdoms, and he agrees to do so.
Qyburn studied to be a maester but wears no chain because the Citadel expelled him fot unauthorized experiments. intrigued by his abilities, Queen Cersei gave him Pycelle's lab and, after Vary's disappearance, named him Master of Whisperers. During Cersei's imprisonment, Qyburn remained faithful to the Queen Mother and helped her execute her plan to destroy the Sept of Baelor. For his loyalty, the new queen appointed him as her Hand.