Claris would use Fire as a Tera-Type,

While Sarin would use Flying as a Tera-Type.

Mariah w Water tera type Samurott 👁👁

Andre w ghost Tera-type Zoroark maybe? 🤔 i think he could come up w some clever tactics with the terastal phenomenon but I’m too smooth brain to come up w anythin atm ;3;

Tera-Grass Corviknight!! J would probably get very excited at the prospect of Mercury joining his Grass-type gang :)

Briar is not into battling but if she had to terastallize a Pokémon, it'd be a fire-type Tera Nickit! So her team is finally full of fire-types

I'm really leaning towards a normal Tera type tinkaton just to fit the type speciality of my oc Smith

Sigurd: Steel

Saki: Poison

Aozame: Water

Dmytro: Tera? What is that? Is that what the youth are using nowadays in battle????

Fuck it.

If Elio knew anything about Terastilizing, then he would use the mechanic for his newly-obtained Miraidon (aka his Rotom Motorbike replacement), turning it into either a pure Dragon-type or Electric-type - depending on the situation.

I'm giving an OC that specializes in fighting and dragon types an Armarouge with the fighting tera type, haha

Balei’s 2 non dragon-like Pokemon would have both be Dragon type!

Fausto would have an Steel type Armarouge with Flash Canon!

Pretty much everyone in Isbar would be using it for the borken meme strats people are using on showdown.
Polly, for example, would be making an electric-tera shedinja with an air baloon.

Fairy.

Avian: Naturally, dragon. It's his corporate-imposed Brand™ after all.

Stahl: Although he has a more mixed team, as a Macro Cosmos rep first and foremost it would be steel.

Arryn terastallizes her Lucario to be pure fighting or steel to max out the damage of Close Combat or Meteor Mash.

Gael would use a Ghost-type Paldean Tauros!! He prolly has at least one on his ranch.

Rani would have a Water-type Cetitan that she could ride during performances while it just spins

Jasmin: Trevenant (Grass)

Andres: Armarouge (Fire)

I have some story stuff set up where Tyler meets a Balloon Pikachu who has the Flying Tera, to pretty much serve as development for Tyler's Phobia of the Pikachu Species. He also uses his Quaxly with the Flying Tera type, that or Water, haven't decided yet-