If a card is Illegal, it means is cannot be used in the official card game at all, not in tournaments, not anywhere. The only exception to this is friendly duels where both duelists agree on the illegal cards in question in terms of their effects. So far, these are the only illegal cards:
English
Asian-English
Japanese
- Black Luster Soldier (normal version)
- Fiend's Mirror (normal version)
- The Creator God of Light, Horakhty
- Obelisk the Tormentor
- Masahiro the Dark Clown
- Slifer the Sky Dragon
- Super War-Lion (normal version)
- The Winged Dragon of Ra
- Tomohiro the Mountain Warrior
- Yasushi the Skull Knight
- Zera the Mant (normal version)