Paradox Brothers

The Meikyū Brothers (Paradox Brothers in the English anime) are antagonists in the Yu-Gi-Oh! anime. They are named Mei and Kyū in the Japanese version, and the kanji of their names form the word for labyrinth. Their English names are Para and Dox, and join to form paradox.

History
The Meikyū Brothers first appear in a cavern on Duelist Kingdom, hired by Maximillion Pegasus as Duelist Eliminators (Player Killers). They challenge Yugi Mutou and Katsuya Jonouchi (Joey Wheeler) to a special tag-team duel that quickly becomes a maze-like movement game when the Brothers summon Labyrinth Wall. Although they nearly win with their Gate Guardian, Yugi and Jounouchi pool their efforts to create Black Skull Dragon to defeat them.

Afterwards, the Brothers allow them to pass, but warn that there are two paths out of the arena: one leads out of the caves, while another leads to an endless maze. As a way of helping the two, the Brothers claim that one of them will speak only lies, while the other will speak only the truth, and furthermore allow both Yugi and Jonouchi to ask one question each to find out which path is correct. However, Yugi deduces that not only are both brothers lying, but in fact they have the power to change which path leads where. By using a two-headed coin to trick the Brothers into admitting this, Yugi and Jounouchi escape the caves.

The brothers also appear in Yu-Gi-Oh! GX as duelling mercenaries that carry their duel against Yugi and Yugi's friend as their only loss. Duelling Jaden Yuki and Syrus Truesdale in a duel to determine if the two are expelled from Duel Academy, the Brothers once again call forth Gate Guardian, but allow it to be destroyed to call forth an even more powerful creature, the sinister Dark Guardian, a monster immune to being destroyed in battle. Much like Yugi's duo before them, Jaden and Syrus pool their efforts to create UFOroid Fighter to defeat the brothers.

Dueling Cards
Note: for aesthetic quality, as well as the fact they only ever duel together, the decks of the Brothers will be listed as one

The Brothers originally played a Labyrinth deck of monsters found in dungeons. Against Jaden and Syrus, they use a deck focusing on summoning the Gate Guardian.

Monster Cards

 * Gate Guardian
 * Sanga of the Thunder
 * Kazejin
 * Suijin
 * Dark Guardian
 * Labyrinth Wall
 * Shadow Ghoul
 * Wall Shadow
 * Labyrinth Tank
 * Dungeon Worm
 * Monster Tamer
 * Jirai Gumo (Landmine Spider)
 * Kaiser Sea Horse
 * Defense Wall

Spell Cards

 * Polymerization (Fusion)
 * Magical Labyrinth
 * Invigoration
 * Remove Trap (Cursebreaker in the Manga)
 * Riryoku (Force)
 * Tribute Doll
 * Dark Designator
 * Monster Reborn (Raise Dead)
 * Fairy Meteor Crush
 * Dark Element

Trap Cards

 * Judgment of Anubis
 * One-on-One Fight
 * Widespread Ruin (Almighty Landmine Claymore)