Citadel of the Autarch, Chapters 27 to 30
Vodalus speak to Severian and is torn between his desire to reward Severian's loyalty and is promise to give Severian up to Agia. Vodalus wants the Autarch delivered to him, and reveals he doesn't know that the Autarch was his servant. Severian is forced to march with the army, and later meets the Autarch again, who relinquishes his life that he may be absorbed by Severian. Severian passes out from the strain of the absorption, and awakes in the clutches of Agia once again, who plans to kill him. However, the Green Man (a time traveller encoutered in Book 2) is there to rescue him. A flying ship arrives and Master Malrubius and his old dog Triskele step out to greet Severian.
[Edited by @Apocryphal]