Leviathan enters the battlefield tapped and doesn't untap during your untap step.
At the beginning of your upkeep, you may sacrifice two Islands. If you do, untap Leviathan.
Leviathan can't attack unless you sacrifice two Islands. (This cost is paid as attackers are declared.)
Near Mint - $0.50
Near Mint Non-English - $0.50
Lightly Played - $0.50
Lightly Played Non-English - $0.50
Played - $0.40
Played Non-English - $0.40
Heavily Played - $0.30
Heavily Played Non-English - $0.30
Damaged - $0.30
Damaged Non-English - $0.30