Cards in set English: 102 | Japanese: 83
Set number English: 20 | Japanese: 22
Release date English: June 14, 2004 | Japanese: Jan. 16, 2004
EX Hidden Legends (Japanese: Undone Seal) is the name given to an Expansion of cards and Theme Decks for the Pokémon Trading Card Game. It completed transferring all of the Generation III Pokémon into card forms.
EX Hidden Legends introduced more dual-type Pokémon, specifically Psychic and Metal. This was the first set since Nintendo took over not to include the Dot-Code data strips on cards, therefore the TCG lost the "e" addition to its name. No set since has featured the technology.
The reverse-holographic design changed in this set. Instead of the previous "plain" holographic design, the same foil was used with an energy symbol pattern. To further distinguish the reverse-holographics and holographics, the type of the Pokémon was displayed as a faint foil symbol in the attack box. The reverse-holographic versions of the holographic rares also have a foil rarity symbol. The reverse-holographic design has changed with every new Expansion since.
The secret box topper for this set is Groudon. The Prerelease card for this set is Swalot. In the United States, Prereleases were held on the weekends of 5th/6th and 12th/13th June 2004.
This expansion finished the process of bringing all Generation III Pokémon into card form, with the exception of Deoxys.