If the Pokémon Darkness Energy is attached to damages the Defending Pokémon (after applying Weakness and Resistance), the attack does 10 more damage to the Defending Pokémon. At the end of every turn, put 1 damage counter on the Pokémon Darkness Energy is attached to, unless it's or has Dark in its name.
Darkness Energy provides Energy. (Doesn't count as a basic Energy card.)
Card text (EX Ruby & Sapphire print)
If the Pokémon Darkness Energy is attached to attacks, the attack does 10 more damage to the Active Pokémon (before applying Weakness and Resistance). Ignore this effect if the Pokémon that Darkness Energy is attached to isn't . Darkness Energy provides Energy. (Doesn't count as a basic Energy card.)
Darkness Energy has been reprinted more often than any other Special Energy card, an honor it shares with Metal Energy.
Neo Genesis - EX Power Keepers print, illus. Milky Isobe
Though both it and Metal Energy represented a type that was eventually as prevalent as the other seven TCG types, only four of this Energy could be included in a deck. This was a major hindrance to the inclusion of Pokémon of these two types in decks until Diamond & Pearl introduced a basic form of this card.
Darkness Energy was introduced to provide Energy for Pokémon of the newly-introduced Darkness-type, which consisted of all Dark-type Pokémon from the games.