Claw of the Conciliator: Chapters 16 to 19
A mysterious blue light wounds Jonas. Severian uses the claw to heal him, and tells an old story from Thecla's book.
Thecla's memories reveal a way out of the antechamber, as the nature of the prison as a former waiting area is revealed. The long-suspected truth about Jonas is also revealed, and he leaves Severian to repair himself.
Severian decides his next task is to recover Terminus Est.