John Scarne's Playing Cards

Origin
John Scarne was a magician and author who loved to manipulate cards and understand how games were played. He learned how to commit cons and the basics of gambling at an early age and put those skills to work as a magician. When not practicing his next trick, Scarne would be reading further about card switches and other sleights of hand. His most famous trick, Scarne’s Aces, involved cutting a shuffled deck to reveal all four aces. He also attempted to discredit the mathematical volatility of Edward O. Thorp's blackjack card counting system, but the participants could never agree upon conditions.

Effects
Performing a riffle shuffle activates all cards within the deck, including jokers. They will float, slide and shuffle to nestle in corners secluded from any opponent’s view. There, they will through some unidentifiable means see and hear what the target is doing and relay that information into the user’s mind. Again, unknown means. All that can be certainly gathered is that the user will know what their adversary is discussing, planning. The user will always feel the need to try and cheat the system, to varying success.