Opposition Agent turns an opponent’s library search into an opportunity for your deck. Its flash ability lets it enter in response to a tutor or fetch-land activation. While an opponent searches their library, you control their choices, and the cards they find are exiled for you to play instead of going to the intended destination.
A fetch-land search still has to find a card meeting its stated requirements. You cannot use a search for a basic land to take an unrelated creature or spell. A broad tutor such as Demonic Tutor offers more choice, while narrower searches make the appropriate part of the opponent’s library available under the original instructions.
The exiled cards can be played for as long as they remain exiled, and you may spend mana as though it were any color when casting them. That permission can provide lasting value after the initial disruption. The Agent does not grant free casting, so expensive spells still require a way to pay their costs, and an exiled land still needs an available land play.
The control effect applies during the search, not to the opponent’s whole turn. Opponents can also respond to the Agent spell before it resolves, and the card does not stop ordinary draws or effects that do not involve a library search. Holding three mana can therefore threaten a specific kind of interaction rather than every form of card selection. Use Agent when searches are common and the deck can capitalize on both the interrupted plan and the cards it gains access to afterward.
