After you log-in, go to My Cards. Click Add Cards. Enter the 10-digit code on the blank space. Ta-Da.
Some cards are free but most of them aren't.
The contest for free The 39 Clues cards expired in 2011. To get cards now, you must purchase them.
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The card that can be used to unlock all 39 Clues Cards is to put in P63726DJXP
I would tell you but not all the clues are out yet. There are 10 clues from all the books (only 6 books are out) and 10 clues from online missions (not all are out yet) and certain cards once you enter them give you clues (all so far are 4 rarity) and card combos (not all card are out yet) JANUS
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There are too many to be solved
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get all of them by going to "My Cards" then go to "Add Cards" and put LuciansRok
These can help actually TRUSTNOONE MANINBLACK that is all i know
Play missions, go in arena 39, and enter card codes to get clues. Get all 39!! ~James the Janus Check out this reusable card code! P3GJW7JEXP
There is no such code, however, by buying cards and completing missions you can get clues. I would post some ultra-rare card codes, but I don't have any that I haven't already used. My top tip is to save your card replicators, because they can be used for those hard-to-find ultra-rare cards. You can give the codes to this site because the codes are reusable.
P4D292PKXP p22229f6xp p222c7pjxp p222hg3dxp p222jcdhxp p44dcx4kxp these are all agent cards this is a non agent card the spaz - g69hjp9g9t
it's technically impossible for me to give you all the card codes cuz someone might have added the codes already but i can give you my agent card code which can be added to your card collection Good luck in your hunt!! my code: P426X3CMXP
You have to add the cards of the books and card packs. Card combos unlock clues. Complete the missions to unlock more clues. When you have all the card combos complete and you have played all missions you will have all the 39 clues. Don't use the replicator cards if not necessary. Use them when you need to unlock a card when it has not been unlocked even after you have added all the cards of the books and card pack.