Players of Pokémon Scarlet and Pokémon Violet can battle Greninja with the Mightiest Mark in two separate time periods: from Friday, January 27th, 2023, at 00:00 UTC to Sunday, January 29th, 2023, at 23:59 UTC, then again from Friday, February 10th, 2023, at 00:00 UTC to Sunday, February 12th, 2023, at 23:59 UTC.

Catch a Greninja with the Mightiest Mark!

Greninja with the Mightiest Mark will be appearing in black crystal Tera Raid Battles! You can try catching Greninja—before it vanishes with a ninja’s grace—first from Friday, January 27, 2023, at 00:00 UTC to Sunday, January 29, 2023, at 23:59 UTC, then again from Friday, February 10, 2023, at 00:00 UTC to Sunday, February 12, 2023, at 23:59 UTC.

Greninja cannot normally be encountered in Paldea, and the Greninja appearing during this event has Poison as its Tera Type, making it a formidable foe—it even has the Mightiest Mark to prove it! Work together with your friends to get the drop on this powerful Tera Pokémon!

This special Greninja can be caught only once per save data. You can still participate in Tera Raid Battles against this Greninja to obtain other rewards if you’ve already caught it.

This Greninja may be featured in future events or become obtainable through other methods.

Strong Foes Make Powerful Allies in the Battle against Greninja!

During this event, you may encounter Bronzong and Lucario in 4-star and 5-star Tera Raid Battles. The Tera Types of these Bronzong and Lucario will vary, and if you catch them, they’ll make powerful teammates in the battle against Greninja with the Mightiest Mark!

Event Schedule

Friday, January 27, 2023, at 00:00 UTC to Sunday, January 29, 2023, at 23:59 UTC
Friday, February 10, 2023, at 00:00 UTC to Sunday, February 12, 2023, at 23:59 UTC

Greninja will have the same mark, Ability, and moves regardless of when it is caught during the event.

Featured Pokémon

7-star Tera Raid Battles: Greninja with the Mightiest Mark
4-star and 5-star Tera Raid Battles: Bronzong and Lucario

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.

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.
• After completing certain postgame events, you’ll be able to find black Tera Raid crystals. However, players who haven’t completed these events may still participate in these Tera Raid Battles by joining other Trainers in multiplayer.
• 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/26.html