Although the other Ultra Beasts never appeared on this planet before the opening of the Ultra Wormholes, inscriptions, folktales, and even court fashions from ancient Johto leave no doubt that Celesteela have been here before. As the tale goes, a single mysterious pokemon, with a metal, narrow body and arms like bamboo shoots, was beloved throughout Johto for its power and beauty. The greatest trainers of the realm – even the emperor – sought to capture the Celesteela, but it was proudly independent and gave its prospective trainers impossible quests. Yet others of its species soon landed and tried to conquer Johto, and after a couple fierce battles in which this Celesteela fought on the human side, it departed with the invaders high into the sky.
The Ultra Crater, home of the Celesteela, is a rogue planet – and as such, it is not a pleasant place to live. Without a stable orbit, the planet is vulnerable to constant meteor bombardment, so Celesteela were forced to evolve metal exoskeletons and narrow bodies to survive. At times, the Ultra Crater itself has come too close to a larger planet or star, and the Celesteela have had to fly out into space to push it into a safe trajectory. The crater's volcanic vents are a poor source of energy, and Celesteela must spend most of their time in hibernation, awakening only when the planet needs moving or they get close enough to a star.
For as long as they were aware of the existence of other worlds, the Celesteela have searched the universe for a new home. Yet curiously, when the Ultra Wormhole opened, the Celesteela did not seek to invade – only visited in small enough numbers at a time that the planet could support them, while treating the experience like a happy distant memory.