Shruikan

Hexproof, Flying, Trample
At the beginning of your upkeep pay {10} or 15 life
If you cannot you lose the game.
If you do double Shruikan's power and toughness
for the rest of the game.
( It stays doubled when Shruikan changes zones.)
{b}{b}{b} Shruikan gets +3/+0 until end of turn.