What is Double Magma Energy?
Double Magma Energy is a Special Energy that was used in the Pokémon Trading Card Game (TCG). It has only been released once – in the XY Double Crisis set of 2015.
See also: What are Special Energy Cards?
The Double Magma Energy card provides two Fighting Energy but can only be attached to a Team Magma Pokémon. The card design features two Fighting Energy symbols.
In the Pokémon TCG, a player can only use an Attack Move if the specified number of Energy are attached. This specified number generally includes one or more Energy that corresponds to the Pokémon type, and / or a number of Colorless Energy. Double Magma Energy Cards provide two Fighting Energy.
Double Magma Energy Card Text:
The text on the card reads:
‘This card can only be attached to Team Magma Pokémon. Discard this card at the end of the turn you attached it.
This card provides 
(If this card is attached to anything other than a Team Magma Pokémon, discard this card.)‘
Gallery
Double Energy Card 34/34 from XY Double Crisis
