Leviathan

Creature - Leviathan 10/10, 5UUUU (9)
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.¹
Illus. Mark Tedin

Gatherer Card Rulings [Nov 2009]

• 10/4/2004: You don't have to pay the untap cost if it is untapped outside the upkeep phase or is untapped by an effect.

Format Legality	Legal in Vintage, Legacy, Extended Banned in Standard
Printings (5/28)	Time Spiral Timeshifted (Special) Beatdown (Special) Fifth Edition (Rare) Fourth Edition (Rare) The Dark (Rare)