Flatten

Flatten is a common Necrobinder attack costing 2 Energy that commands Osty to deal 12 damage, but costs 0 Energy if Osty has already attacked this turn. This conditional discount rewards Osty attack chains, providing substantial damage for free after any other Osty attack.

Flatten is free after Poke's zero-cost Osty attack, creating a 0-Energy chain dealing 18+ total Osty damage. Sic 'Em's Summon triggers on Flatten's Osty hit, and Rattle's multi-hit counts Flatten as another prior Osty attack. Calcify adds 4 damage to Flatten's already-large 12 base.

In the Necrobinder Osty/Summon archetype, Flatten is a core damage card that turns Osty chains into devastating bursts. Against any boss, a Poke into Flatten sequence deals 18 damage for 0 Energy, which is among the most efficient damage in the game. With Calcify, this becomes 22 damage for free. Building your deck to consistently enable Flatten's free condition maximizes the Osty archetype's damage output.