This event was released to celebrate the launch of Pokémon Scarlet and Pokémon Violet. Players could acquire the event codes in selected stores around the globe.
Even if the official release date was meant to be September 16, 2022, some users were able to obtain the event codes days before. Those codes couldn't be used until September 15, 2022, when the wondercard was made available in the servers.
Wonder Card ID #1643: Shiny Etern