
Whenever a creature an opponent controls diesdiesA creature dies when it goes from the battlefield to a graveyard. Being exiled or returned to hand is not dying., exile it with a hit counter on it.
Assassins, Mercenaries, and Rogues you control have deathtouch and "Whenever this creature deals combat damage to a player, you may remove a hit counter from a card that player owns in exile. If you do, draw a card and create two Treasure tokensTreasure tokensA Treasure is an artifact token with ", Sacrifice this token: Add one mana of any color."."
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Read from the rules text. A card that enables a keyword makes or is the thing; a card that rewards it gets better when you have it. Two cards interact when one enables what the other rewards.