The official Pokémon website has announced that Tyranitar, Togekiss, Rotom, Dragapult and Excadril will appear more frequently in Max Raid Battles in Pokémon Sword and Shield until May 11th, 2020, at 4:59 p.m. PDT.

Tyranitar, Togekiss, Rotom, Dragapult, and More in Max Raid Battles

Track down and catch these powerful Pokémon in the Wild Area in Pokémon Sword and Pokémon Shield.

Some popular Pokémon are taking over the Wild Area in Pokémon Sword and Pokémon Shield. Be on the lookout for Tyranitar, Togekiss, Excadrill, Whimsicott, and Dragapult appearing more frequently in Max Raid Battles until May 11, 2020, at 4:59 p.m. PDT. Also during this time, Wash Rotom will appear in Pokémon Sword Max Raid Battles and Heat Rotom will appear in Pokémon Shield Max Raid Battles.

To challenge these Pokémon in a Max Raid Battle, you'll need to connect your Nintendo Switch system to the internet. Then, whenever you see a pillar of light shining from a Pokémon Den in the Wild Area, you can walk up to the Pokémon Den and interact with it to start a Max Raid Battle with a Dynamax Pokémon.

Source: https://www.pokemon.com/us/pokemon-news/tyranitar-togekiss-rotom-dragapult-and-more-in-max-raid-battles/