Emerald is a set in the EX series. It was released on May 1, 2005. The printed size is 106. This checklist is longer, at 107 cards. Double Rainbow Energy is 87/106, in position 87 of 107 on this checklist. Before it is 86 Darkness Energy, and after it is 88 Metal Energy. The listed rarity is Rare.
Double Rainbow Energy is an Energy card. It is listed as Special.
Takumi Akabane illustrated this card. The same name is on 51 other cards in the catalog.
The card text says: Double Rainbow Energy can be attached only to an Evolved Pokémon (excluding Pokémon-ex). While in play, Double Rainbow Energy provides every type of Energy but provides 2 Energy at a time. (Has no effect other than providing Energy.) Damage done to your opponent's Pokémon by the Pokémon Double Rainbow Energy is attached to is reduced by 10 (before applying Weakness and Resistance). When the Pokémon Double Rainbow Energy is attached to is no longer an Evolved Pokémon, discard Double Rainbow Energy.
I keep a set binder for Emerald, meant to hold every card of that set. This card is one slot in the Emerald set binder. I still need this card.