River Fiend

River Fiend's power is equal to the number of
lands in your graveyard.
Whenever River Fiend attacks you may pay {x} and sacrifice any number of lands. If you
paid {u} and sacrificed an Island, draw 2 cards.
If you paid {b} and sacrificed a Swamp, destroy
target creature.

Also known as the "Dragon of Goonch," it is as
lovely as it is voracious.
And it is very voracious.