Permafrost Trap
Permafrost Trap {2}{U}{U}
Instant - Trap
If an opponent had a green creature enter the battlefield under his or her control this turn, you may pay {U} rather than pay Permafrost Trap's mana cost.

Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.
Latest set: [WWK] Worldwake (U)