Submerge 
Instant
If an opponent controls a Forest and you control an Island, you may cast this spell without paying its mana cost. Put target creature on top of its owner's library.
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL