Legendary Creature â Human Spy
As long as X is in X's owner's opponent's hand, X's owner may cast X and activate X's abilities. That opponent can't cast X and plays with their hand revealed.
, : Put X into target opponent's hand.
: You may play a land or cast a spell from the hand X is in. If you cast a spell this way, you cast it without paying its mana cost.
Dmitry Burmak INTERVIEW
You play the card as Xâ€™s last ability resolves, with one exception: You canâ€™t play a land this way unless itâ€™s your turn and you have an available land play. If youâ€™re casting a spell this way, you do so as the ability resolves. Ignore any timing restrictions based on the cardâ€™s type. You can cast their sorceries or creatures during their turn, for example.
You donâ€™t own the cards you play this way. An instant or sorcery cast this way will go to its ownerâ€™s graveyard. A creature card you cast this way will enter the battlefield under your control, but it will be put into its ownerâ€™s graveyard if it dies. The same is true for other permanent cards you cast or lands you play.
You choose which card to play as Xâ€™s last ability resolves. Your opponent can respond to you activating the ability to get other cards out of their hand. Whateverâ€™s left when the ability resolves is fair game.
You activate Xâ€™s first activated ability while X is on the battlefield under your control. This puts X into an opponentâ€™s hand. That opponent plays with their hand revealed, and theyâ€™re not allowed to cast X or activate any of Xâ€™s abilitiesâ€”but you are. You can activate Xâ€™s second ability to play one of the cards in that hand.