When cards of unknown origin begun to appear across Equestria, incidents begun to arise related to their appearance. While most are harmless, a few of the cards ended up corrupting the personality of those who touched them, attempts to stop them proved to be fruitless as the corrupted ponies kept on saying they could only be stopped in a duel.

Princess Celestia, the ruler of Equestria, casted a spell on one of the cards in hopes looking into their purpose and find a solution in the process. The spell backfired and she ended up warping a scared pony with a backpack in front of her. Much to her surprise, the pony claims himself to be a being known as a human named Dusk from a world known as Earth.

Celestia was more surprised when Dusk showed her the contents of his backpack; containing a unknown object and multiple deck of cards with the back design being the same as the ones that appeared in Equestria. He explained that he plays a popular card game known as Duel Monsters and he was packing his Duel Disk and his cards for a tournament prior to being warped.

Celestia realize she may have unexpectedly brought forth the solution she was seeking...

(An alternative universe Yu-Gi-Oh/MLP story)