Pokemon Scarlet and Violet's Terastallize mechanic makes Pokemon shiny and changes their type

gamesradar.com:

Pokemon Scarlet and Violet has a new Terastallize mechanic that makes each 'mon shinier than Shinies and temporarily changes their typing. 

The "mysterious Terastal phenomenon" was shown off during today's Pokemon showcase. Terastallize is similar to the Mega Evolutions and Gigantamax forms of previous games; it's a temporary power-up that enhances a Pokemon's moves. But instead of making them bigger, it gives Pokemon a gemstone-like reflective shell – and a fancy hat, it seems, with the starters sporting some elemental chandeliers in the trailer.  

"Players can Terastallize a Pokémon once per battle and the transformation will last until the battle ends," an explainer reads. "Players will need a Tera Orb to Terastallize a Pokémon, which will need to be recharged after each use. Players can charge their Tera Orb by touching crystals overflowing with Terastal energy or by going to a Pokémon Center."

All of the Pokemon in the new Paldea region can use Terastallize, The Pokemon Company explained, and some even have different Tera types. A normal-type Eevee may have grass or water-type Tera forms, for example, while Pikachu can gain a flying type referencing the balloon Pikachu from the original Pokemon Snap. There are a total of 18 Tera types in all. 

Terastallize is also core to the raid battles of Pokemon Scarlet and Violet. Like Pokemon Sword and Shield, you have a better chance to find stronger Pokemon, now including those with rarer Tera types, via raids which you can tackle with friends. Tera Raid Battles promise to be a bit faster-paced than the Gigantamax raids of Sword and Shield, though, since everyone can act independently without worrying about turn timing. 

Here's everything we learned about Pokemon Scarlet and