The Mega Diancie ex Mega Battle Deck focuses on Mega Diancie as the central Pokémon, released in this deck as a Psychic-type Mega Evolution Pokémon ex card. The deck includes cards from the Phantasmal Flames expansion, with its two highlight cards being Mega Diancie ex and Meloetta, the latter of which is included as both a standard card and an MEP Promo-exclusive illustration rare card. It is the international equivalent to the Japanese MEGA Starter Set Mega Diancie ex product, which was released in Japan on September 5, 2025.