This is a wild area event held by Sword and Shield. This event does not have any Gigantamax Pokémon encounters.
This wild area event seems to feature favorites used in online battles, such as Tyranitar, Excadrill, Whimsicott, Togekiss, Dragapult and Rotom.
To import these files into your save, use PKHeX's block importing function. Our tutorial should guide you through it.
Our first post of this page would contain some data relevant to the importing stage.
There's info and some common questions regarding Wild Area Events here.
To see other Wild Area Events, here.
In about 9 hrs, they fixed the 1 star Drilbur on Shield: It no longer gets Hydro Pump (Index 19 -> Index 20)