Best case scenario, you draft Druddigon as your active Pokémon on first turn.

Tank with Druddigon and build up your Greninja while landing cheap shots using Darkrai’s ability.

Once you’re set, either wait for your Druddigon to be knocked out or, if you have enough tempo advantage, specially against slower decks, retrieve your Druddigon once your Darkrai has three energies and start hitting 100 damage each turn, or even 120 damage if you have Greninja on your bench.