Gregor's condition continues to deteriorate. The venom turns the blood in Clegane's body black and any leeches that touch him die instantly. His piss is full of pus, and the venom eats a hole the size of a fist in Clegane's side. His screams of agony are so loud they can be heard in the entire
Red Keep, and even wake several people up during the night.
Qyburn states upon examining him that it is a wonder the man is still alive, to which
Cersei Lannister replied,
“Gregor is a very large man. Also a very stupid one. Too stupid to know when he should die, it seems.”
Insensible and dying, Gregor is brought to the dungeons below the Red Keep, where his screams can no longer be heard, by
Qyburn, who is allowed to experiment on him before his impending death. According to Qyburn the poison was
manticore venom thickened with sorcery to draw out the Mountain's dying instead of killing instantly.