Tera has been with Casey ever since it was a Toxel. One year prior to the start of the Sword & Shield arc, Tera was used to battle illusions of Zacian and Zamazenta, only to get knocked out and get separated from its Trainer.
Later, Tera was found in Glimwood Tangle chasing a wild Dreepy that it was dead-set on battling, along with the Dreepy's caretaker, a wildDrakloak. Drakloak initially had the upper hand, but with the help of Casey, Tera defeated the Drakloak with Snarl and rejoined Casey's team.
Tera was later used as Casey's final Pokémon in her Gymbattle against Opal and her GigantamaxAlcremie. Casey intended to have Tera Dynamax, but was shocked and pleased to see that it had Gigantamaxed. She had Tera use G-Max Stun Shock on Alcremie, which poisoned the Cream Pokémon. In response, Opal made Alcremie use G-Max Finale, and although the G-Max Move was not very effective on it, Tera got confused by the high-calorie cream missiles. This caused Tera to hurt itself and knock itself out, thus losing Casey the match and eliminating her from the Gym Challenge.
Personality and characteristics
Tera has a tendency to show off to people that it hasn't seen in a while, as shown when it pretended to not notice Casey and her Arrokuda, Kilo because it wanted to beat Drakloak. Like most Low Key Form Toxtricity, Tera holds its strength in high regard, and so, it has a habit of getting angry when opponents that seem weak at first glance actually turn out to be quite formidable. When Tera sweats poison, it gets agitated from the pain caused by the sweat. The more agitated Tera gets, the more it sweats, getting it even more agitated. This process eventually leads to Tera developing tunnel vision and being unable to hear anyone.
