What makes you think that there is one. All that happened was Drifter added one card to what was on the table. There's no rules to be garnered from that and indeed no rules you need to invent for that.
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It's actually common for writers to make things like that, and it would be reasonable given the direction Destiny has taken in storytelling to assume there might be. As the current trend is every scene is filled with a bunch of little items and lore, that you later collect cards on, and read about.
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Yea the shadow just hated the card he placed and drew on him.