Players of Pokémon Scarlet and Violet can catch a Mewtwo with the Mightiest Mark in black crystal Tera Raid Battles from Friday, September 1st, 2023 to Sunday, September 17th, 2023, at 23:59 UTC.

Prepare to Face a Mighty Mewtwo!

Catch a Mewtwo with the Mightiest Mark! Mewtwo with the Mightiest Mark will be appearing in black crystal Tera Raid Battles from Friday, September 1, 2023, at 00:00 UTC to Sunday, September 17, 2023, at 23:59 UTC.

Mewtwo cannot normally be encountered in Paldea, and the Mewtwo appearing during this event has Psychic as its Tera Type. Be prepared—this Pokémon is a formidable foe, and it’s got the Mightiest Mark to prove it! Work together with your friends to topple this powerful Tera Pokémon!

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

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

Event Schedule

Friday, September 1, 2023, at 00:00 UTC to Sunday, September 17, 2023, at 23:59 UTC

Featured Pokémon

7-star Tera Raid Battles: Mewtwo with the Mightiest Mark
Strong Foes Make Powerful Allies in the Battle against Mewtwo!
Prepare to face Mewtwo with the Mightiest Mark by participating in other Tera Raid Battle events leading up to the appearance of this Legendary Pokémon. With some powerful allies by your side, you’ll be ready to take on Mewtwo at black Tera Raid crystals!

Prepare the Offense: Event Schedule
Wednesday, August 9, 2023, at 00:00 UTC to Thursday, August 17, 2023, at 23:59 UTC

A Show of Supporters: Event Schedule
Friday, August 18, 2023, at 00:00 UTC to Thursday, August 31, 2023, at 23:59 UTC

Prepare the Offense and A Show of Supporters: Encore Event Schedule
Friday, September 1, 2023, at 00:00 UTC to Sunday, September 17, 2023, at 23:59 UTC

What Will Happen When Mew Faces Mewtwo?

Something special might happen if you send Mew into a Tera Raid Battle against Mewtwo, so train up your very own Mew and challenge this Mewtwo with the Mightiest Mark!

You can add Mew to your team by entering a password via Mystery Gift. For more details, please visit the official Pokémon Scarlet and Pokémon Violet site.

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 participate in Tera Raid Battle events, please 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/119.html