From Friday, December 9th, 2022, at 00:00 to Sunday, December 11th, 2022, at 23:59 UTC, players of Pokémon Scarlet can participate in Tera Raid Battles featuring Tyranitar and players of Pokémon Violet can participate in Tera Raid Battles featuring Salamence.

Challenge Tyranitar and Salamence Now!

Turn Strong Foes into Powerful Allies! You have until Sunday, December 11, 2022, at 23:59 UTC to challenge these fully evolved Pokémon in Tera Raid Battles! Tyranitar is appearing more frequently in Tera Raid Battles in the Pokémon Scarlet game and Salamence is appearing more frequently in Tera Raid Battles in the Pokémon Violet game. These Pokémon will have various Tera Types, so prepare wisely before challenging them!

Event Schedule

Friday, December 9, 2022, at 00:00 to Sunday, December 11, 2022, at 23:59 UTC

Featured Pokémon

Pokémon Scarlet - 4-star and 5-star Tera Raid Battles: Tyranitar
Pokémon Violet - 4-star and 5-star Tera Raid Battles: Salamence

What Is a Tera Raid Battle?

In a Tera Raid Battle, you’ll work together with three other Trainers to defeat a powerful Tera Pokémon before time runs out. The kinds of Pokémon encountered during Tera Raid Battle events will vary. Pokémon encountered in Tera Raid Battles may have a rare Tera type.

Check the Poké Portal for more information about what Pokémon are appearing in Tera Raid Battles.

Information about Tera Raid Battle Events

• To encounter Pokémon featured in Tera Raid Battle events, you need to have downloaded the latest Poké Portal News. Poké Portal News will automatically download if your Nintendo Switch™ system is connected to the internet. You can also download the latest Poké Portal News by selecting Poké Portal from the X menu, then Mystery Gift, then Check Poké Portal News. You do not need a paid Nintendo Switch Online membership to receive the latest Poké Portal News.
• A paid Nintendo Switch Online membership (sold separately) is required to participate in Tera Raid Battles with other Trainers online. Terms apply.

Source: https://sv-news.pokemon.co.jp/en/page/13.html