Demon Series

The "Demon Series" (悪魔シリーズ Akuma Shirīzu) is, as the name suggests, a series of cards used in Yu-Gi-Oh! Duality of Demon by various characters, and are a primary plot point.

Design
All members of the Demon Series are based on the Lesser Keys of Solomon of demonology (the study/belief of demons). In their card forms, they all appear in different representations of the demons they are based on.

Role in Duality of Demon
In the Yu-Gi-Oh! Duality of Demon, cards of the Demon Series are known to posses strong powers both in and outside of Duels. Owners of cards in the Demon Series are known to posses the ability of "Demonize", which allows them to summon their respective monsters into the real world, making their forms, attacks, and to an extent, their effects real. Battle (outside of Duels) often take place between owners, with the loser often submitting to the victor's wishes. Cards of the Demon Series are also known to possess an excessively large amount of power, that most can only be in possession of one of them at a time. Effects of possesing more then one include loss of sanity, being taken over by the power of the card, or even death in some cases. One exception being the protagonist, Yuda Amuka, who is shown to be able to hold multiple cards of the Demon Series without any side effects. Why he is able to do so is currently unknown.

Members
All of the currently known cards of the Demon Series along with their reference and owner are listed here:

Trivia

 * The Demon Series was partially based off of the "" archetype from "".