Triton-Bane Leviathan

Islandwalk, Menace
When Triton-Bane Leviathan enters play, it gets
-1/-1 for each non-Island land you control.
Leviathan's Hunger—At the beginning of combat,
you may sacrifice a Merfolk. If you do, target land becomes an Island. If you don't, tap Triton-Bane Leviathan. It doesn't untap during it's controller's
next untap step.