Propulsion engineer Cheng Xin is the protagonist of Death’s End and the author of A Past Outside of Time, excerpts from which are integrated as chapters into the novel. Throughout the narrative, Cheng Xin jumps in time, often hibernating for decades or even centuries. Becoming a globally influential person because of the star Yun Tianming gifts her, Cheng Xin envisions herself as a protector and guide for humanity, taking on responsibility for the fate of humanity. When she runs for the position of Swordholder, she does so from a globally maternal perspective: “A young mother came up to Cheng Xin and handed her baby, only a few months old, to her. [...] Her heart melted, and she felt as if she were holding a whole world, a new world as lovely and fragile as the baby in her arms” (145). The sense of duty of thus parenting all humans follows Cheng Xin throughout her life; the public often looks to her in crises, such as when she averts war between Wade’s Halo Company and Bunker World.

Though Cheng Xin spends much of the novel burdened by duty, she is a dynamic character who eventually realizes that she need not feel responsible for the entire species.