Saving Stow-on-Side Gym

Walkthrough
By heading next to the Stow-on-Side Gym next with Piers and Hop, you will learn from either Bea or Allister (depending on the version you're playing) that multiple Pokemon are now Dynamaxing at the hands of Sordward and Shielbert. Because of this, each of you will have to defeat one of the Dynamaxed Pokemon in a Max Raid Battle all by yourself. In Pokemon Sword, the Dynamaxed Pokemon will be a Level 62 Conkeldurr, one that will know the moves Thunder Punch, Ice Punch, Hammer Arm, and Stone Edge (also being able to use the Max Moves associated with each of those attacks). In Pokemon Shield, the Dynamaxed Pokemon will be a Level 62 Dusknoir, one that will know the moves Thunder Punch, Ice Punch, Earthquake, and Shadow Punch (also being able to use the Max Moves associated with each of those attacks).

After helping clear the Gym of all the Dynamaxed Pokemon, you will receive Bea's/Allister's Rare League Card.