Counters

What is a Counter Card?: A counter card is defined as any card played or discarded from hand that cancels/negates one or more effects of a just played card or that cancels/negates a just played card itself. In addition, counter cards ignore printed phase requirements for being played/discarded from hand provided that the appropriate effect that they would counter has occured. Note that allies must still be played into battle unless otherwise stated.

What about cards that are in play?: Any card that is already in play is subject to the "I'm in play first so I get to use my power first" rule and is not considered a counter card, though its abilities may have one or more effects that are "counter card-like."
What about cards that redirect, replace, retarget or prevent an effect? Cards that redirect, replace, retarget or prevent the effect of another card are normally not counter cards because they do not cancel/negate a card that is granting the effect. In these cases, the
card granting the effect is considered to have been played and resolved successfully, though the outcome of its effect is modified from what the card intends.