The Seal of Orichalcos (UDE promo)

Despite what most people think, THIS CARD DOES EXIST. There are only 15 copies in existance, all in the possession of members of Upper Deck Entertainment's R&D division, who used them in the Decks they played in the Orichalcos "Duel the Master" side event at previous National Tournaments.

In the anime, "The Seal of Orichalcos" was used by the forces of Dartz in the Doma ("Waking the Dragons") story arc. It also took the soul of the duel's loser so it could be used to resurrect the Great Leviathan.

Notes: Other non-gameplay effects that occured in the anime were:
 * Neither player could leave the Duel, and no other player could enter the field (unless the person wishing to break the Seal possesses a fragment of the Orichalcos Stone, which can break this enchantment. However, Yugi's Millennium Puzzle was able to break the Seal on one occasion.).
 * The losing player wouldn't lose their soul under 3 conditions: *1. One player uses the orichalcos stone immediately, ending the Duel. * 2. Both players Life Points reach 0 at the same time, resulting in a Draw. *3. The controller of this card begins acting 'purer', such as giving up their Life Points to save their monsters. Note that this condition applies only if the controller loses. It is unknown whether the opponent would be spared.
 * The player playing The Seal of Orichalcos, along with the monsters on his/her side of the field, will bear the Symbol of Orichalcos on their forehead, perhaps as a sort of mockery against the Millennium Symbol. The Symbol of Orichalcos controls their mind and mainpulates them to be evil. The Darkness is infused within the player's body causing them to be full of anger and hatred, which is showed through their glowing red eyes.