The August trailer for Pokemon Scarlet and Violet revealed the new gimmick for the upcoming Gen 9 games to be Terastallization, a phenomenon that grants trainers in Paldea to change the type of their Pokemon once per battle. The way Terastallization works is that all existing types a Pokemon might have before it Terastallizes are removed in favor of the critter's Tera type, which can be the same as one of the Pokemon's base types or any other existing type in the series. This means that Pokemon Scarlet and Violet's battles could be even more exciting than in the past thanks to the many strategies one can employ with Terastallization, both offensively and defensively.
The latest trailer for Gen 9 games featured a battle against one of Pokemon Scarlet and Violet's Gym Leaders, in this case, the Grass-type specialist by the name of Brassius. The short clip provided fans with many useful pieces of information, such as the fact that Gym Leaders can also have an ace that is not from Gen 9, and also that they use Pokemon that don't necessarily have the same type as their specialization, which is normally something Champions are expected to do. In the trailer, Brassius also lets his Sudowoodo Terastallize into a Grass-type Pokemon, which on one hand makes sense, on the other, it means that Gym battles could be even easier than expected.
Why Pokemon Scarlet and Violet's Gym Battles Could be Easy
Brassius Terastallizing Sudowoodo into a Grass-type could be written off as a coincidence, but the fact that the trainer has a line of dialogue specific to this Pokemon means that the Gym Leader is always going to use Gen 9's gimmick in this way. This can be problematic because Sudowoodo is normally a pure Rock-type critter, which deals supereffective STAB damage to Flying, Bug, Fire, and Ice-type pocket monsters. These are all types that, in turn, deal supereffective damage to Grass Pokemon.
As such, in every battle against Brassius, Pokemon Scarlet and Violet players can safely use Flying, Bug, Fire, and Ice Pokemon to deal with the Gym Leader's team and his ace because Sudowoodo will always Terastallize into a Grass-type, becoming weak to their attacks. Brassius' ace Pokemon will likely retain Rock-type moves that will still deal decent damage to Pokemon they are supereffective against, but they will always lose their STAB multiplier, which is wasted potential in this fight. This also makes Brassius' use of the Terastal phenomenon ineffective, strategy-wise.
The problems Brassius' Sudowoodo will have are likely going to be shared by other Gym Leaders, and the Grass-type specialist's use of Terastallization will probably resemble that of other Gym Leaders. Instead, Pokemon Scarlet and Violet's Terastallization could have been used much more effectively by the AI by allowing Gym Leaders not to have a fixed Tera type for their Pokemon that matches that of their Gym, but rather use types that normally resist attacks that could easily beat their specialization. For example, the aforementioned Sudowoodo could Terastallize into a Rock-type, which it already is, meaning that it would not only retain the usual STAB damage of its moves but gain a buff to it.
A degree of versatility here could make each Gym battle more exciting and refreshing, rather than a scripted encounter that one can cheese through by using Pokemon that deal supereffective damage against the Gym Leader's specialization. This also removes all the benefits from having particular Pokemon on the Gym Leader's team that are naturally dual-types, as any offensive or defensive benefit from those types will always be lost via Terastallization. Overall, Pokemon Scarlet and Violet's current system seems to make sense from a thematic standpoint, but it does lower the difficulty of Gym battles by quite a lot.
Pokemon Scarlet and Violet are set to release on November 18, exclusively for Nintendo Switch.