FrostStrike
From The Bakugan Wiki
(Opposing Flip Cards cost 1 more for each point of FrostStrike on this Bakugan on Victor) ‘’’FrostStrike’’’ is a Combat keyword in the ‘’Bakugan Battle Planet’’ game. Flip Cards will cost 1 additional for each point of the (Opposing Flip Cards cost 1 more for each point of FrostStrike on this Bakugan on Victor) the attacking Bakugan has.
If you have a Flip Card that has an effect that plays the card for free such as Pact of Darkness, then FrostStrike still applies and raises the cost depending on how much FrostStrike you have.