EX Power Keepers is loosely based around the Hoenn Elite Four; Sidney, Phoebe, Glacia, and Drake. They each have their own Stadium Card, and the Pokémon-ex featured in the set are all Pokémon owned by them in the games. Some Pokémon in the set have attacks that are enhanced when a particular Elite Four Stadium card is in play. The set was conceived to fill the gap between EX Dragon Frontiers and Diamond & Pearl, due to Nintendo's continuing trend of releasing expansions in time with related games.
With no Japanese set at the time to correlate with EX Power Keepers, Nintendo created many new cards, making this set the first since Team Rocket to use original cards created outside of Japan. As a result, many cards feature artwork by Ken Sugimori (as his Pokémon character images are used widely in other media and are readily available) plus background images edited with filter effects from various sources.
In Japan, the set was available only through the Pokémon Card Game website, in a similar fashion to the distribution of the Pokémon Web expansion. Released under the name of World Champions Pack, it was intended for Japanese players only so they would not be at a disadvantage at the 2007 World Championships. Japanese players could order their packs online from June 15 until July 1, a rather limited window of opportunity. Packs were released from July 5 onwards to those who had ordered them. Each pack contained fifteen cards as opposed to ten.
- Several cards in the set are reprints from older sets with new artwork, bringing back old favorites to once again see tournament play. These cards include:
- Blaziken (reprint from EX Ruby & Sapphire)
- Combusken (reprint from EX Ruby & Sapphire)
- Delcatty (reprint from EX Ruby & Sapphire)
- Gardevoir (reprint from EX Ruby & Sapphire)
- Slaking (reprint from EX Ruby & Sapphire)
- Omastar (reprint from EX Sandstorm)
- Wobbuffet (reprint from EX Sandstorm)
- Magneton (reprint from EX Dragon)
- Machamp (reprint from EX Hidden Legends)
- Lanturn (reprint from EX Hidden Legends)
- Ninetales (reprint from EX Hidden Legends)
- There are no Half Decks to correlate with the Japanese release.
- The elusive Eeveeloutions make their English debut in this set, previously only available as Japanese PLAY Promotional cards. To the disappointment of players and collectors, only Flareon, Jolteon, and Vaporeon were released, but Espeon and Umbreon later appeared in POP Series 5, albeit in non-holographic forms.
- At the time of its release, EX Power Keepers finally brought the number of sets released in English and in Japanese equal once again, but with its Japanese release the sequence was again thrown out of balance.
- Despite already being available as PLAY promotional cards in the past, the Japanese set still includes the Eeveelutions , allowing players not in the Players Club or those who did not gain enough EXP Points for these cards a chance of obtaining them again.
- This is the first time an entire English-exclusive expansion has been translated into Japanese. Previously, only single cards had been translated from English into Japanese, such as Dark Raichu from the Team Rocket expansion and several cards from EX Sandstorm.
- The prerelease card for this set is Cacturne.