Qyburn

At the Citadel, Qyburn earned a name as a fine healer in Archmaester Ebrose's eyes. That wasn't enough for him: instead of studying life by cutting open the dead, as maesters had for centuries, he started cutting open the living to understand death. Once word got out, they stripped his chain for experimenting on people.

With no trade and no Citadel, joining the Brave Companions was the only way out. Of his old life, the only man he still respects is Archmaester Marwyn, the one who shared his curiosity about what lies past death; the rest of the archmaesters he simply calls "the grey sheep."

When the Brave Companions switch sides and hand Harrenhal over to Roose Bolton, Qyburn takes on the duties of the previous maester, Tothmure, executed for sending ravens to King's Landing. Gendry hears whispers that this stranger knows dark magic and necromancy.

When Jaime Lannister is brought to Harrenhal a prisoner, Bolton puts him in Qyburn's care, and his skill keeps the wound from costing Jaime the whole arm. When Jaime is sent south to his father, Qyburn goes along; before leaving he sends the servant girl Pia to Jaime's chamber, hoping to win Lannister favor, though Jaime doesn't touch her.

Qyburn leaves the Brave Companions behind and settles into the court at King's Landing, where he talks Cersei into letting him experiment on a dying Gregor Clegane. He earns her trust the ugly way: putting his knowledge to work torturing prisoners.

He suspects Oberyn Martell poisoned his spear to drag out Clegane's death. Once the Mountain's death is confirmed, he prepares the skull to be sent to Dorne. Cersei rewards him with the seat Varys left behind when he vanished: Qyburn becomes Master of Whisperers, with a voice on the small council.

With the queen's blessing, Qyburn keeps testing things in the black cells on the prisoners and enemies handed to him; the subjects rarely come out of it well. Behind it all sits one standing project: building Cersei an invincible champion, for which he commissions armor too large for any ordinary man.

When Lady Falyse Stokeworth comes to Cersei in despair after her plot against Bronn falls apart, the queen hands her over to Qyburn to be rid of her. Later, asked whether she's still alive, Qyburn says yes, though "not entirely comfortable," and no longer fit to rule Stokeworth; he adds that he's learned a great deal from her.

After the Faith arrests Cersei, Qyburn manages to visit her cell and brings her up to speed on everything that's happened, including his own removal from the small council. He tells her the champion is ready to defend her, but Cersei reminds him that only a knight of the Kingsguard can stand for her in trial by combat, so she has a letter sent to Jaime.

Qyburn is at the Red Keep when Cersei finishes her walk of atonement and meets her new champion, freshly sworn into the Kingsguard after Ser Arys Oakheart's death: "Ser Robert Strong." Off the council or not, Qyburn still runs the eunuch's network of little birds, and according to Kevan Lannister he now holds the keys to the cells where Margaery Tyrell's supposed lovers are kept.