The card system is introduced in the second Pimpernel book: Royal Ball. it is never fully explained by any character, but we become more familiar with characters who are new to it.
The system categorizes every human on the planet as a card from a normal playing deck, and every character in the Pimpernel world has a designation … except for a few outliers who have yet to be defined by the system. (Hint: Z is one of them.)
In cases of royalty, status is determined by bloodline and aptitude. For everyone else, it is based on capability and actions taken on the world’s playing board.
There are more players for each card than most people would care to count. It’s a big, big world out there, and — as you can see below — we are only beginning to meet all the players in the game.
Note: An ellipsis (…) marks cards with no confirmed characters, but that does not mean that no such character is on the page. It just means they are not confirmed as that card. Feel free to guess if you think someone belongs somewhere!

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Arin Yalin

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Elliot Church

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Dr. Matthews

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Claire Ramsey

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Sebastian Kahn

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Ren

Jack Cavanaugh

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Wanda

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General Zao

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Tiki

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Margot (Queen heir)
Selene

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Abed

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Anila

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Augustus

Arthur

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Ace (AI)
Wild Cards
Wild cards always come in pairs. They are power players with opposite aims. One will win; one will lose, but you will never know what game they’re playing until it’s through.

Osment/Malachi