"Forbidden One" , known as "Sealed" (封印されし Fūinsareshi) in Japanese, is an archetype of DARK Spellcaster-Type monsters released in Legend of Blue Eyes White Dragon with its first support released as a Weekly Shōnen Jump promotional card in 2007. "Forbidden One" was one of the first Deck themes, and it still remains a popular one.

While many people refer to the "Forbidden One" cards as "Exodia" cards, the "Exodia" archetype is a separate but related archetype, and the only "Forbidden One" card to be a part of it is "Exodia the Forbidden One" (the head).

"Exodia" (エクゾディア, Ekuzodia) was, at first, a beast of such incalculable and intimidating might that he was split up into five distinctive parts, each one of them chained and sealed away by magic from all the other monsters (hence "the Forbidden One"). That would have prevented his power from ever being used again.

Shimon used Exodia against Zorc Necrophades, against whom he was equal; however, "Exodia" was defeated because he drew his power from Shimon, a single mortal man, whereas Zorc had his own power source.

As a result, in the Yu-Gi-Oh Card Game, there are five distinct "Forbidden One" cards, each one symbolizing a part of the complete "Exodia". In order for "Exodia" to regain his tremendous power, all of the five cards must be reunited in the player's hand. This brings the parts of the "Forbidden One" together, allowing "Exodia" to break free, his strength being so great that he guarantees the player an automatic win, regardless of the situation.

The effect of "Exodia" makes it one of the most godlike monsters in Duel Monsters; unlike most monsters, "Exodia" doesn't rely on ATK and DEF, instead causing an immediate victory when all five cards are assembled in the hand.