A folk tale story emerged, called "Starship Steela". Landing from the moon, an old couple found the Pokémon and thought it was a shining bamboo sprout. As it grew, the nearby bamboo sprouts began to wither and fade, prompting the local villagers to attack. The old couple attempted to protect Steela, who revealed itself as large spaceship and flew off. After its' departure, more bamboo sprouts began to grow.
Sophocles, wondering if the story was true, finds Celesteela by chance after going down a slope that lacked bamboo trees. However, he noted the "sprout" was actually metal and when the moon shined while the sky is clear on its face, it smiled. Sophocles soon informed his friends of his discovery, and they partially dig out Celesteela.
Based on the data Sophocles found while digging out Celesteela, it has stored a massive amount of gas and was likely to depart soon, burning everything below it. The group managed to create a rock wall with their Pokémon to stop the stored gas from burning the local bamboo fields. Despite Team Rocket's attempts to shatter the wall to capture the Pokémon as part of their benefit chances to be the "True" Team Rocket, Celesteela flew off into space.
None of Celesteela's moves are known.