Goblin Moneylender

Haste
{t}: Add two mana in any combination of colors
to your mana pool. At the beginning of your next upkeep, you may pay {3}. If you don't, exile the top ten cards of your library.
Oh, don't worry 'bout payin' us back our coin
too much. We'll make sure we gets it back, one way,
or anotha'.