A new Max Raid event has begun in Pokemon Sword and Shield. To commemorate Pokemon Day, the Legendary Mewtwo is appearing in Max Raid dens for a limited time, as are the original three starter Pokemon, Bulbasaur, Charmander, and Squirtle--and you'll get some great rewards for defeating them.
The Mewtwo Raid in particular differs from other Raids in a few ways. First, Mewtwo is uncatchable. Before you join the Raid, you'll see a warning that Mewtwo can't be caught, but there's still a good incentive to battle it; you'll receive some fantastic rewards if you can defeat the Legendary, including Ability Capsules--which can be used to change one of your Pokemon's Abilities.
Earning these rewards won't be easy, however. Mewtwo is level 100, and it's incredibly fast and powerful; it can move four times in a turn and knows a broad range of attacks. The Kanto starters, however, can be caught. These Raids likewise dispense rare items as rewards, including Flame Orbs, which could previously only be obtained from Sword and Shield's true antagonist, the Ball Guy.
The special Max Raid event will only be live for a few days, ending at 3:59 PM PT / 6:59 PM ET on March 1. You can read more details on the official Pokemon website. There's also still some time left to catch Gigantamax Toxtricity and the other G-Max Pokemon that are currently spawning more often, including Kingler, Grimmsnarl, and Hatterene.
In other Pokemon news, The Pokemon Company unveiled a brand-new Mythical Pokemon for Sword and Shield: Zarude. Not much is currently known about the new monster, but it's a Dark/Grass type that has the Ability Leaf Guard. It also plays a role in the upcoming Pokemon film, Coco, which premieres in Japan this July. Armored Mewtwo has also returned in Pokemon Go as part of that game's Pokemon Day event, and this time it's accompanied by Clone Pokemon.