Chassellon Stevis originated from Coruscant, a planet, and was a male human. His mother held the position of head of the Coruscant diplomatic legation. In the year 3 BBY, Stevis participated in the Apprentice Legislature, sharing a pathfinding class with Leia Organa. During their initial pathfinding session, Harp Allor, a fellow Apprentice Legislator, injured her ankle. Stevis made the decision to abandon her to avoid expulsion from the class.
Upon his return to the pathfinding chalet, Stevis discovered that Harp was already present, enjoying mocoa with Organa and the other classmates who had remained to assist her. Subsequently, Chief Pangie issued a reprimand to Stevis for his abandonment of Harp.
Stevis continued his service in the Apprentice Legislature alongside Organa, which included a visit to the Emperor's Museum. He also chose to remain silent when he observed Organa suspiciously attempting to secure passage off Coruscant on the vessel Mighty Oak Apocalypse. Previously Stevis had been trying to hire the ship to take him to a speeder auction on Arkanis. Later, Stevis was present at the ceremony where Organa was officially invested as crown princess of Alderaan, offering her a wink as she passed. Amilyn Holdo of Gatalenta, another Apprentice Legislator, was also in attendance.
Organa and her father both noticed that he possessed a certain arrogance, which they considered a typical Coruscanti characteristic. His interest in purchasing and restoring vintage speeders led Organa to realize that he had a greater capacity for patience than she had initially assumed.
The first appearance of Chassellon Stevis was in Leia, Princess of Alderaan, a young adult novel from 2017 penned by Claudia Gray, which was launched as part of Journey to Star Wars: The Last Jedi. While the novel describes Stevis as having dark skin, the colored illustrations in the manga adaptation depict him with decidedly light skin, contrasting with the black and white pages that portray him with light dark skin.