As is customary with every new set of mainline Pokemon games since Generation 6, Pokemon Scarlet and Violet have their own region-exclusive battle gimmick: the Terastal phenomenon. Terastallization was revealed in Pokemon Scarlet and Violet's third trailer, and it's an interesting mechanic in that it allows players to change the types of a Pokemon to its Tera type, which can be any of the existing 18 types in the games. This tool will be extremely versatile in many Gen 9 battles, as players have control over how and when to use it for both offensive and defensive means.
Because Terastallizide Pokemon can become either a completely new type or use the Terastal phenomenon to empower one of its existing types, this can be used as a strategic means to make some bits of the games easier, or as a tool to change one's team composition. It's possible that Pokemon Scarlet and Violet's Terastallization will have problematic use cases due to the way the games are designed, yet it can be both good or bad for the team-building process in Gen 9, which means that players should pay close attention to the way Terastallization functions.
Why Terastallization Can Be Both Good or Bad For Team Compositions
Pokemon Scarlet and Violet's Paldea region will be seemingly completely free to explore, with no restrictions on where to go first and what sort of Gym to undertake, which is a revolutionary approach for the series. However, it also means that Gen 9 will be much harder to balance in terms of battles, as Gym Leaders need to have teams that can scale up or down depending on the players' level. So far, Gym battles have been a staple of the series to challenge trainers by using specially trained teams of Pokemon who share one main type for each Gym.
Terastallization in Pokemon Scarlet and Violet could cause issues because every Pokemon will be able to access any Tera type the player seeks out, and then potentially access a Tera-type STAB move that every creature can learn according to recent leaks. In theory, Gen 9 teams could forego one important part of planning encounters by using the Terastal phenomenon to always have a type advantage with a Pokemon or two against every Gym, trivializing these battles in the long run.
While this may be bad for the games, there is a noteworthy silver lining here due to how team composition can benefit from the versatility of the Terastal phenomenon. Players could more freely choose their Pokemon based on which creatures they like best without fear of limitations imposed by their type combinations, as having multiple critters on the team that share the same type becomes less worrisome in Gen 9. Terastallizing any pocket monster in Pokemon Scarlet and Violet can make up for bad match-ups, or it can help trainers overcome battles where their critters would have major type disadvantages.
Strategy-wise, Pokemon Scarlet and Violet will implement a gimmick that can reach its full potential in the endgame, where having fully-trained Pokemon with multiple non-STAB moves to cover diverse type combinations is often crucial. This also applies to PvP, as Terastallizing Pokemon can lead to more unpredictable battles where planning ahead is much more valuable to seize victory. There will likely be scenarios where Terastallization is problematic in Pokemon Scarlet and Violet, but there are also benefits that greatly exceed those of past gimmicks like Mega Evolutions.
Pokemon Scarlet and Violet launch on November 18 for Nintendo Switch.
