Limbo

{t}: Flip a coin. if heads, add one mana of any color. If tails, add two mana of a random type.
{5}, {t}: Create a 1/1 colorless Elemental sliver creature token. Activate this ability only if you control a Sliver.
At the beginning of the end step, you may flip a coin. If you flip a coin and it lands on heads, you win the game. If you flip a coin and it lands on tails, you lose the game.