Sorcery, 3U (4)
Common
Target player puts the top X cards of his or her library into his or her graveyard, where X is the number of lands you control.
Stray into the Morkrut and it may rise to claim you.
Illus. Cliff Childs

5/1/2012: The number of cards put into the graveyard is based on the number of lands you control when Dreadwaters resolves.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Extended (Type 1.X)
Legal in Standard (Type 2)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern