Where do you get dubious Disc in Pokemon tower defense 2?

In Pokémon Tower Defense 2, you can obtain the Dubious Disc by defeating the boss in the Sinnoh region's Distortion World. After defeating this boss, the Dubious Disc has a chance to drop, allowing you to use it to evolve certain Pokémon like Porygon into Porygon-Z. Make sure to engage in battles in this area to increase your chances of acquiring it.