[[Spanish release date::| ]][[Spanish Sneak Peek date::| ]] [[English release date::| ]] The Lost Millennium is a Booster Pack in the Yu-Gi-Oh! Official Card Game (OCG) and the Yu-Gi-Oh! Trading Card Game (TCG). It is the fourth Booster Pack in the OCG Series 4. This set has been released in the TCG in English, French, German, Italian, Portuguese and Spanish and in the OCG in Japanese, Asian-English and Korean. Its main focuses are on Rock-Type monsters and the archetype "Elemental HERO", capitalized "Elemental Hero" at the time. It also introduced several cards used in the Yu-Gi-Oh! GX series.