Keldon Berserker 

Creature — Human Soldier Berserker
Whenever this creature attacks, if you control no untapped lands, it gets +3/+0 until end of turn.
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Cards that do something similar expected a card that isn't here?
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Terra Ravager 89%
$0.06#25564
"Whenever this creature attacks, it gets +X/+0 until end of turn, where X is the number of lands defending player controls."
Reckless Ogre 84%
$0.12#31389
"Whenever this creature attacks alone, it gets +3/+0 until end of turn."
The Long Reach of Night // Animus of Night's Reach 80%
$0.22#11099
"Whenever this creature attacks, it gets +X/+0 until end of turn, where X is the number of creature cards in defending player's graveyard."
Reckless Pangolin 80%
$0.12#31018
"Whenever this creature attacks, it gets +1/+1 until end of turn."