Charmed Pendant

{t}, Put the top card of your library into
your graveyard: For each colored mana
symbol in that card's mana cost, add
one mana of that color to your mana
pool. Play this ability only any time you
could play an instant. (For example, if
the card's mana cost is {3}{u}{u}{b}, you add
{u}{u}{b} to your mana pool.)