Summoning Trap

Oracle Text

If a creature spell you cast this turn was countered by a spell or ability an opponent controlled, you may pay 0 rather than pay Summoning Trap's mana cost.

Look at the top seven cards of your library. You may put a creature card from among them onto the battlefield. Put the rest on the bottom of your library in any order.

Card Rulings

10/1/2009 You may ignore a Trap’s alternative cost condition and simply cast it for its normal mana cost. This is true even if its alternative cost condition has been met.
10/1/2009 Casting a Trap by paying its alternative cost doesn’t change its mana cost or converted mana cost. The only difference is the cost you actually pay.
10/1/2009 Effects that increase or reduce the cost to cast a Trap will apply to whichever cost you chose to pay.
10/1/2009 If there are seven or fewer cards in your library, you’ll look at all of them.