Ghastly Moat

Whenever fortified land becomes tapped, target player puts the top card of his or her library into his or her graveyard.
Whenever an Island or Swamp enters the battlefield, you may attach Ghastly Moat to it.
Fortify {3} ({3}: Attach to target land you control. Fortify only as a sorcery. This card enters the battlefield unattached and stays on the battlefield if the land leaves.)