Hamustra was a librarian and floor manager of the Tower who collected ruined or nearly destroyed stories—apocalypses—and selected hunters to save them. Though content with his role, he secretly longed to one day appear inside a story as a character rather than as an overseer.

While observing countless worlds, he became aware of the Constellation Killer, a being whose sole purpose was to kill constellations. From that moment, his dream twisted into wanting to be killed by the Constellation Killer, believing that such an end would allow him to exist meaningfully within a story.

That changed when he met Kim Gong-ja. Impressed by how Kim Gong-ja overcame every trial and treated the people within ruined stories with genuine care, Hamustra came to regard him as his favorite protagonist. Upon their meeting, Kim Gong-ja decided to give him a new purpose by selecting an unfinished story, [The Epic of Lefanta Aegim], as the theme of the Tower’s 29th floor.

This choice caused an error: Kim Gong-ja was sent directly to the Constellation Killer—who was in fact Lefanta Aegim, also known as Kim Yul. Kim Gong-ja successfully killed him, but the Tower corrected the mistake and replaced the floor’s official story with [The Tale of the Ascending City].

During this corrected scenario, Kim Gong-ja summoned a new version of Kim Yul—one who had repented for his past and chose to live differently. He then forced Hamustra to choose between this reborn Kim Yul and the original Constellation Killer. Upon choosing the repentant Kim Yul, the original Constellation Killer was reduced to an insignificant extra, and Hamustra’s desire to die by his hand vanished along with his life’s purpose.

Having foreseen this outcome, Kim Gong-ja offered Hamustra a different path: to appear in a story not through death, but by living—by climbing the Tower alongside him. Though bound by a contract to the Tower Master, Hamustra ultimately accepted. Breaking that contract stripped him of all authority and reduced him to an ordinary person.

Hamustra then began a new life as a normal human, working at the Library Café Planetarium on the 30th floor of the Tower—finally existing within a story, not as a librarian of endings, but as a character himself.