The Red Keep's dungeons had four levels in total. The top level, or first level, contained cells with narrow, high windows, used to hold ordinary criminals.
The second level consisted of small individual cells for noble captives. Being underground, torches constantly burned in the hall of the second level, their light shining through the bars to illuminate these solitary cells.
The third level had no windows and no torchlight. Its cells had sturdy wooden doors, and the criminals within were imprisoned in darkness at all times. Thus, they were called the "Black Cells."
The Black Cells held the most wicked and dangerous criminals, and the guards paid no heed to whether they lived or died.
These prisoners either starved, died of thirst, froze to death, or were driven mad by the endless darkness.
Clack!
An empty cell in the Black Cells was opened, and a blazing torch tore through the endless darkness.
Rattle, rattle, rattle!
The appearance of that light stirred a series of shifting chains throughout the Black Cells.
"Hiss, hiss!"
"Pretty boy, come in here. I'll make you feel amazing."
Robb followed Varys down the corridor of the Black Cells. In the cells on either side, two hideous prisoners pressed their faces against the small windows in the wooden doors and made noise at him.
"Tsk, tsk, how interesting. One man has two faces; surely such a man should serve the Many-Faced God."
Varys had long grown accustomed to the prisoners' racket and strode ahead, but a sentence from one of the cells made Robb stop.
He turned to look and saw a handsome man with red-and-white hair smiling at him.
Jaqen H'ghar, one of the Faceless Men of Braavos. He had helped Arya and set her upon the path of the Faceless Men.
Robb certainly had not