Anyone familiar with the core RPG Pokémon games will know about Hidden Abilities.
Starting in the fifth generation, most Pokémon were given an additional ability known as a Hidden Ability. This feature returns in Pokemon Sword and Shield, but the way in which you acquire Pokémon with this ability is completely different.
The only way to get Pokémon with Hidden Abilities this time around is through Max Raid Battles. Raids can be started through the Pokémon Dens in the Wild Area that emit a red beam of light. You can take part in raids with AI players, friends, or random players online.
When you defeat a Pokémon in these raids and capture them, sometimes they’ll have their Hidden Abilities. This is random, however, and there’s no guarantee that the Pokémon you’re fighting will have one.
So if you want to secure some Hidden Abilities, prepare to grind.