Hello again! You may have noticed that I didn't mention Terastallization in my last post while talking about potentially banworthy things in the metagame. The reason being
I forgot I felt that the topic deserved it's own post, as I plan to go into a lot of detail here. I don't have much else to say here, let's get into the actual post.
Terastallization is this generation's gimmick, and it allows you to change the type of one of your Pokémon every battle. This gimmick has no inherent drawbacks such as requiring an item slot, and unlike Mega Evolutions and Z Moves, you can Terastallize any of your Pokémon and not just one designated Tera Pokémon. This makes Terastallization similar to Dynamax in the sense that you can use it on different Pokémon depending on what matches up best into your opponent. Its applications are equally diverse, with it being a great offensive and defensive tool. Additionally, you can Terastallize into a type you already have to receive a STAB bonus of 2x. This could be considered unhealthy due to the inherent unpredictability and variance that comes with allowing any Pokémon to be any type. Giving any Pokémon adaptability is also quite a worrying thought considering all of the monstrous offensive powerhouses added this generation. The purpose of this post is to give some of my own opinions on Terastallization and some cool ways I believe it could be used.
Prominent Users
This format has been out for a week at the time of writing this, so it's pretty early to say what the best users of Terastallization are yet, as several applications of it have most likely gone undiscovered at this point in time. Despite this, I'll still take this time to highlight some offensive and defensive uses of Terastallization that stand out to me.
Offensive Uses
Flutter Mane
Flutter Mane is by far the most broken offensive user of Terastallization. Being able to Terastallize into a pure Fairy type to power up your already very strong Dazzling Gleams as well as remove your weakness to Ghost-type attacks for the mirror is insane on a Pokémon with Flutter Mane's stats. I don't think Terastallization is the problem here, however. Flutter Mane is an extremely good user of it, but that's moreso because Flutter Mane is broken rather than the gimmick itself being problematic.
Chi-Yu
Chi-Yu is the only other debatably broken user of Terastallization. Tera fire Heat Wave hits extremely hard, especially when boosted by Torkoal's Drought on the Sun teams it frequently finds itself on. Removing its Dark typing also has some niche defensive applications, like being able to take Fighting-type attacks more easily. Chi-Yu is undeniably an amazing example of an offensive Terastallization user, but Terastallization doesn't fix any of Chi-Yu's flaws as a pokemon, it just boosts it's already insane damage output, which is a common theme with using Terastallization to boost a type you already have.
Dragonite
Dragonite is my personal favorite offensive use of Terastallization. Tera normal Extreme Speed hits extremely hard for a priority move, making it an insane late game sweeper allowing it to ignore all current speed control active. Dragonite also has great offensive coverage outside of Extreme Speed, making it a great offensive asset overall. You don't even really need to run speed on it because of Extreme Speed's high priority bracket, allowing you to invest more in bulk and allow Dragonite to work in and out of Trick Room. While I personally think this set is amazing, it's not without counterplay. You essentially don't have a tera Pokémon if your opponent has means of blocking priority, and you're giving up your great defensive typing in Flying/Dragon for pure Normal, meaning you also lose your Earthquake immunity.
Brute Bonnet
Brute Bonnet is interesting because it's Terastallization options also have utility defensively. There are the obvious options of Grass and Dark to power up it's stabs, but it can also run Tera Fighting. Fighting resists nearly all of it's natural weaknesses and gives you a stronger Close Combat, which is nice in this format because of the amount of Dark-types.
Slither Wing
Slither Wing has some interesting options for offensive Terastallization. Again, the obvious options of Bug for strong First Impressions and U-Turns and Fighting to power up Close Combat are still there, but it also has more interesting options like Fire on Sun teams to boost Flare Blitz to insane levels and Ghost with Tera Blast, which gives you unresisted Ghost/Fighting coverage (though admittedly at that point you're most likely better off using Annihilape outside of Sun teams)
Defensive Uses
Glimmora
Glimmora is the premier Hazard Stack Pokémon in SV DOU. It can set hazards without actually having to waste turns setting them with it's ability Toxic Debris. It has a 4x weakness to Ground however, which is a problem in this meta because Earthquake finds itself on nearly every team. Tera Flying can be used to give yourself an Earthquake immunity to not only give yourself a partner to click Earthquake next to, but are also immune to opposing Ground-type attacks, which can catch opponents off guard and allow it to set more layers of Spikes.
Wo Chien
Wo-Chien is a fairly niche pick in the current meta, but it has it's uses. Specifically Tera Water with Leech Seed. Water doesn't have much synergy with it's original typing of Grass/Dark, Water is just a solid defensive typing that lets it survive longer to click it's support moves. It functions pretty similarly to support Tapu Fini sets from the last generation and fits very nicely on hazard centric teams.
Arcanine
Arcanine's main defensive Tera options are Water and Grass. Grass is nice to hit Ground, Rock, and Water-types with Tera Blast and also gives you an Earthquake resist. Water also resists or is at least neutral to a lot of Arcanine's natural weaknesses as a pure Fire-type. Water/Fire coverage is also extremely good neutral coverage on most things. Arcanine isn't a Pokémon you want to Terastallize in a lot of matchups, but it's nice that it has such solid options if it does find itself in a situation where it needs to Terastallize for whatever reason.
Gothitelle
Gothitelle isn't a Pokémon that you'll see Terastallize very often, but it does have some decent options. Tera Fairy allows Gothitelle to resist most moves that it would otherwise be weak to (other than Ghost-type attacks which become neutral) making it a nice defensive option. Tera Normal is an option that allows it to more easily sponge hits from Flutter Mane, which is very valuable. Gothitelle has some respectable Terastallization options, but you generally don't want to waste Terastallization on a Pokémon as passive as Gothitelle.
Gyarados
Gyarados's Water/Flying typing synergizes perfectly with Ground type Tera, and has offensive and defensive utility. Defensively, you resist everything that Gyarados would otherwise be weak to, and offensively your Earthquakes hit that much harder, which Dragon Dance sets greatly appreciate. Gyarados is a great candidate for Terastallization in most matchups, and has proven itself to be one of the best uses of the gimmick.
Final Thoughts
As for my full thoughts on Terastallization, I believe it's a good, healthy addition to the meta and adds a new dimension to the game that's really interesting to explore both in teambuilding and gameplay. You could argue that Terastallization causes unnecessary variance due to the fact that any pokemon can become any type, but I don't think this is the case. I would actually argue that Terastallization rewards good, creative teambuilding. If I use Tera Grass Arcanine to beat my opponent's Ting-Lu for example, I not only had to have saved my Terastallization up until that point in order to use it to beat my opponent's Pokémon, but i also had to have intentionally chosen that tera type in the builder to deal with that specific Pokémon while being aware of the opportunity cost that comes with that. Personally, I think that's an extremely healthy and balanced dimension to add to the game. There are some Pokémon that are broken with Terastallization, like Flutter Mane and debatably Chi-Yu, but those Pokémon are largely broken because of outside factors unrelated to Terastallization. Like, Flutter Mane would still be broken regardless of whether or not it could Terastallize. But that's just my opinion, which ultimately probably doesn't really matter, but I thought i would share it anyway. Alright, that's all I have to say, have a damn good day (or night, idk when you're reading this) :D