If an opponent had two or more creatures enter the battlefield under their control this turn, you may pay {U} rather than pay this spell's mana cost. Return two target creatures to their owners' hands.
2009-10-01
Casting a Trap by paying its alternative cost doesn't change its mana cost or mana value. The only difference is the cost you actually pay.
2009-10-01
Effects that increase or reduce the cost to cast a Trap will apply to whichever cost you chose to pay.
2009-10-01
You can target any two creatures, not just ones that entered this turn.
2009-10-01
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.
2009-10-01
You must target two creatures as you cast Whiplash Trap. If you can't (because just one creature is on the battlefield, perhaps), you can't cast the spell.