Gangrenous Zombies

{T}, Sacrifice this creature: This creature deals 1 damage to each creature and each player. If you control a snow Swamp, this creature deals 2 damage to each creature and each player instead.

Masters Edition II

{T}, Sacrifice Gangrenous Zombies: Gangrenous Zombies deals 1 damage to each creature and each player. If you control a snow Swamp, Gangrenous Zombies deals 2 damage to each creature and each player instead.

Coldsnap Theme Decks

Ice Age

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T: Sacrifice Gangrenous Zombies to have it deal 1 damage to each creature and player. If you control any snow-covered swamps, Gangrenous Zombies instead deals 2 damage to each creature and player.

Whether it does 1 or 2 damage is checked on resolution.