Leviathan

Creature - Leviathan 10/10, 5UUUU (9)
Trample
Leviathan comes into play 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

Crystal Keep Rulings Summaries

• You don't have to pay the untap cost if it is untapped outside the upkeep phase or is untapped by an effect. [Duelist Magazine #3, Page 7]
• To make it attack, the two Islands are sacrificed at the time it is declared as an attacker. This is an increase to the cost to attack. [D'Angelo 1998/06/05]
• Note - Also see Trample, Rule 502.9.

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)