What is Mystery Energy?
Mystery Energy is a Special Energy that was used in the Pokémon Trading Card Game (TCG). It has only been released once – in the XY Phantom Forces set of 2014.
See also: What are Special Energy Cards?
The Mystery Energy card provides one Psychic Energy but can only be attached to a Psychic type Pokémon. The card design features the Psychic Energy symbol.
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. Mystery Energy Cards provide one Psychic Energy.
Mystery Energy Card Text:
The text on the card reads: ‘
This card can only be attached to 
Pokémon. This card provides Energy, but only while this card is attached to a Pokémon.
The Retreat Cost of the Pokémon this card is attached to is 
less.
(If this card is attached to anything other than a Pokémon, discard this card.)‘
Gallery
Mystery Energy Card 112/119 from XY Phantom Forces
