Jokulmorder 
Creature — Leviathan
Trample This creature enters tapped. When this creature enters, sacrifice it unless you sacrifice five lands. This creature doesn't untap during your untap step. Whenever you play an Island, you may untap this creature.
Legality
standardNOT LEGALpioneerNOT LEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL