Leviathan
Leviathan {5}{U}{U}{U}{U}
Creature - Leviathan | Power/Toughness: 10 / 10
Trample
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.)
Latest set: [TSB] Time Spiral "Timeshifted" ( S · #23 )