Worldwake Spoiler - 魔法風雲會

http://forums.mtgsalvation.com/attachment.php?attachmentid=100768&d=1264490303
Permafrost Trap 2UU
Instant — Trap (Uncommon)
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.

剋色陷阱系列，限制一定有用；構築不一定。

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