Conclave's Pact

Conclave's Pact is green and white.
Tap any number of untapped creatures you
control. Search your library for a creature card
with converted mana cost X or less, where X is
the number of creatures tapped this way, and
put that card onto the battlefield. Then shuffle
your library.
At the beginning of your next upkeep, pay {1}{g}{w}. If you don't, you lose the game.