DLC in Pokemon Plus and Minus

Here is the downloadable content available for Pokemon Plus and Minus. (not just mythical Pokemon)

Mythical Pokemon

 * Cheatress: A Gamestop event Pokemon available October 2019, part of the promotion of the 22nd Pokemon movie. After you get it from a delivery man at the Pokemon Center, a man dressed in black will instantly arrive and give you the Eternal Booster. The Eternal Booster will allow Cheatress to achieve his Impossible Forme. He is Level 50, and is holding a Metro Bomb.
 * Uniking: A Gamestop event Pokemon available October 2020, part of the promotion of the 23rd Pokemon movie. After you enter the code, you don't receive the Pokemon from the delivery man directly. Instead, you get the key item Demon Crown. To get Uniking, head to Necro Citadel, go to a strange tomb, and use the Demon Crown to awaken Uniking himself! And then you can fight and catch him. He is Level 80, the most powerful Pokemon in the region!!!
 * Plexicus: A Gamestop event Pokemon available October 2021, part of the promotion of the 24th Pokemon movie. If you have obtained the DNA Splicers in Pokemon Time Diamond and Space Pearl, you can use them to merge Plexicus with Uniking to let it achieve its Plexiking Forme. That merging feature is not available in Pokemon Plus and Minus.