Dark Amulet Deck Cases were created by the P.L.O.O.P. members in order to take over the world.
These amulets are also known as Evil P.L.O.O.P.Y. Deck Cases.
These dark amulets were created in the mines at the Valley of Dim close to the gates of the Dark Civilization land, where an unlimited amount of dark power is available. P.L.O.O.P experimented on the deck cases to force creatures to lose control over their actions and give control of these creatures to the amulet holders. They plan to take over both the creature world and real world with these amulets.
The original form of these deck cases were the Amulet Deck Case's which are used to calm down creature and also to help train duelists to become the True Kaijudo duelists. P.L.O.O.P. came up with a plan to reverse this process using dark energy to make creatures go berserk instead but this was not enough for Prince Maurice, the Merciless. Maurice created a way to mass produce these amulets cloning them, enough for each member of the P.L.O.O.P. army to control these creatures.
In the end of the Sacred Lands season, the P.L.O.O.P. army fought against Shobu and his friends Hakuoh, Kokujo, Mimi and George in a Kaijudo duel and lost. They continued to use the power of the dark amulets but they began to self-destruct because of the overuse of their dark power.
Creatures from the Fire Civilization gate had already started to invade the city in the real world as they were still under the influence of the dark P.L.O.O.P power. These fire civilization creatures were managed to be controlled by the elite JDC duelists with Amulet Deck Cases from the JDC Headquarters.