The Wishing Star (Japanese: ねがいぼしWishing Star) is a Key Item introduced in Generation VIII. It is a source of Dynamax energy, which can be fit into a Dynamax Band in order to allow a Trainer to Dynamax their Pokémon. According to Professor Magnolia, the Wishing Stars are parts of Eternatus, which is said to have some sort of connection to the Dynamax phenomenon.
Spoiler warning: this article may contain major plot or ending details.
In Pokémon Sword and Shield, two Wishing Stars fall from the sky near the player and Hop after their battle on Route 2. Professor Magnolia then takes them and fits them into Dynamax Bands for the two. Bede is later revealed to be collecting Wishing Stars for Rose, gathering them from Galar Mine and Galar Mine No. 2. He also attempts to destroy the famous mural in Stow-on-Side to get more of them. During the game's climax, Rose reveals that Macro Cosmos has been giving the gathered Wishing Stars to Eternatus in order to solve the energy crisis that is facing Galar in one thousand years.
During the post-game, Sonia is revealed to hold the Wishing Stars confiscated from Chairman Rose after his arrest at her laboratory. They're later stolen by Sordward and Shielbert with the help of Sonia's treacherous assistant in order to advance their plans.
Two Wishing Stars appeared in Ooh Shiny!! Legendary Equipment. One year before the arc's events, Casey and Henry saw two Wishing Stars falling into the Slumbering Weald, and entered the forest to find them. With the help of Henry's Farfetch'd, they eventually found them, and, as thanks for the help, Casey gave one of them to Henry. They were later fitted into Dynamax Bands for the two Trainers.