Corrupt

Sorcery    (CMC:6)

Corrupt deals damage equal to the number of swamps you control to target creature or player. You gain life equal to the damage dealt this way.

124 7E • ENScott M. Fischer

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Legal in: Modern,Lorwyn-Shadowmoor Block,Urza Block,Legacy,Vintage,Freeform,Prismatic,Tribal Wars Legacy,Singleton 100,Commander

Oracle Text (click to copy):

10/4/2004
The swamps are counted on resolution.
8/15/2010
The life you gain is equal to the damage dealt by Corrupt, not necessarily to the number of Swamps you control (if some or all of the damage is prevented, for example).
8/15/2010
The amount of damage dealt to a creature is not bounded by its toughness, and the amount of damage dealt to a player is not bounded by that player's life total. For example, if Corrupt deals 6 damage to a 2/2 creature, you'll gain 6 life.
7/1/2013
Corrupt counts any land you control with the subtype Swamp, not just ones named Swamp.