The Mega Evolution Build & Battle Box was released as a prelude to the Mega Evolution expansion and offered people the opportunity to experience the cards before their general release on September 26, 2025. Tournaments were typically held on the weekends of September 13-14 and September 20-21, 2025. Boxes could also be purchased from stores in the Prerelease Program from September 13, 2025.
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Each box included a ready-to-play 40-card deck plus four Mega Evolution booster packs to potentially integrate useful cards into it. Starting with the Mega Evolution expansion, Build & Battle Box decks are built around only one archetype, instead of the combined two archetypes from previous Build & Battle Box decks. Each Mega Evolution Build & Battle Box deck includes a promotional card, and an assortment of Pokémon, Trainer cards, and Energy cards themed around the promotional card. The possible promotional cards include Meganium, Inteleon, Alakazam, and Lunatone. Mega Evolution Build & Battle Boxes were categorized as Play Level 2.
The boxes could provide exclusive Non Holofoil versions of cards only available as Holofoil in Mega Evolution booster packs: Meganium, Xerneas, and Hariyama.
Box structure
Each box included one of the following four different decks.