Sacrifice is an ever-present theme in the novel. The first sacrifice is Richard’s engagement to Jessica. He chooses to help Door even when Jessica threatens to end the relationship, though it may be argued that this is not really self-sacrifice because their relationship is somewhat toxic. After that, Anaesthesia is taken by the darkness when she and Richard cross the bridge to the Floating Market. Hunter tells Richard that it is a toll some must pay, and he understands that the rat-speakers sent her as his guide because she was expendable. This inspires Richard to risk his own safety on multiple occasions: when he and Door come face to face with Mr. Croup and Mr. Vandemar in the British Museum, when Door is captured after Hunter’s betrayal, and when Islington wants Richard tortured to get Door to cooperate. The Marquis also sacrifices himself on more than one occasion, most valiantly when he goes to question Mr. Croup and Mr. Vandemar and loses his life in the process. The idea of self-sacrifice is also allegorical, referring to Jesus Christ, who died for the sins of humanity and may be on the other side of Islington’s prison door.